This is a detailed description of the new daedric birthsigns. Note that minor powers have a 100% of casting in all situations, and major powers may only be cast once per day. Attributes are damaged 1-10 points on using some daedric powers, but this can be amplified by weakness to magicka.

ASHPIT CURSE - MALACATH
NEVERENDING ASHSTORM (ability) Nerfs: start your game with endurance and luck damaged 30 points,  sound 15 points(distracts the character from spellcasting), blind 25 points (blinds the character and makes you miss in combat). Buffs: willpower (15), agility (20), strength (25).
SCOURGE OF THE ASHPIT (major power) on self for 120 seconds: blind 20-30, sound 20-30, fortify speed 25-50. on target for 120 seconds: blind 50-80, sound 50-80, drain attribute speed 25, demoralize creature 8 points. Costs intelligence to use.
CHALLENGE TO A DUEL (minor power) absorb on touch longblade, axe, blunt, endurance, and luck for 15 seconds. Costs endurance to use.
COUP DE GRACE (minor power) on touch weakness to normal weapons and magicka, damages strength and intelligence. Costs luck to use.
PLAYSTYLES: Malacath is the patron deity of the Orsimer, so Orc is a natural choice. This birthsign is a low-health challenge. The traditional fighter builds of Warrior, Knight, or Crusader would be thematic. Archer is, in my opinion, the perfect fit for this birthsign: spear for endurance and range, marksman to pepper your enemies from afar, and restoration to cure your attributes. The Imperial Cult and Legion are factions friendly to Orcs, and grant access to many restore attribute options. Scourge of the Ashpit is a crowd control option, slowing down your enemies while speeding you up.
Recommended Mods: Modern Combat is recommended for this birthsign, allowing dynamic health: health is figured dynamically, instead of at your character generation and level ups, which has the advantage of not penalizing you for not achieving +5 endurance every early level up. Crossbows Enhanced is recommended for their awesome Orcish Crossbow design.

BASTARD OF SANGUINE
WILD EYES (ability) Nerfs: 125% weakness to fire and frost, 75% weakness to common disease, start the game with willpower damaged 25 points. Buffs: +35 personality
ALLIES OF EXCESS (major power) summon ancestral ghost (55), scamp (50), dremora (45), and clanfear (40 seconds).
SUMMON DRINKING BUDDY (minor power) summon scamp (60 seconds), drain Willpower on self 60 seconds.
WALK OF SHAME (minor power) fortify unarmored 175 points for 120 seconds, drains athletics and personality for 120 seconds.
DRUNKEN SPEECH (minor power) rally humanoid and creature 1-100 points for 60 seconds, drains intelligence and willpower for 60 seconds.
PLAYSTYLES: summoning allies and buffing them, drinking alcohol to fortify willpower after using powers, and wearing fashionable clothes. Almost any race or class could benefit from these powers, but the weaknesses may mean your character is best behind the front lines. Since using your powers hurts your ability to use spells, the classes Acrobat, Monk, and Thief are recommended. They all share a skill in Unarmored, giving them more use from Walk of Shame. They also lack offensive spells, summons, and buffing spells for allies, making this birthsign a good fit.

BLESSING OF BOEHTIAH
BAD BLOOD OF BOEHTIAH (ability) Nerfs: weaknesses to poison 125% and magicka 75%. Buffs: luck (10), strength (20), and endurance (30).
HUNGER OF UPRISING (major power) all for 120 seconds: summon Hunger, restore health 2-6 points, fortify agility 50 points, weakness to poison 50%, weakness to magicka 25%. Costs endurance to use.
PLAYSTYLES: warriors and fighters who want passive, useful bonuses will appreciate Boehtiah. The handy power will make you almost unstoppable, but the cost to endurance makes alchemy or restoration almost essential. Bards, archers, spellswords, battlemages, and assassins all have these skills. Whatever the class, the huge boosts to useful stats makes this a tempting sign.

DREAMWEAVING OF VAERMINA
WAKING NIGHTMARE (ability) Nerfs: weaknesses to fire, frost, shock, poison, normal weapons, and magicka 50% each.
DREAMSCAPE (minor power) sanctuary 75 points for 30 seconds, restore magicka 5-15 points for 20 seconds, blind 25 % each for 15, 10, and 5 seconds, invisibility 20 seconds. Costs strength to use.
SLEEP OF THE OLD HAG (minor power) on self for 3 seconds: summon three Winged Twilights. On touch for 5 seconds: blinds 50-100. On touch for 30 seconds, drain fatigue 50-100, drain agility 50-100. Costs luck to use. 
PLAYSTYLE: mages and spellcasters of all types will appreciate the unlimited well of magicka they can draw from when entering the dreamscape. Traditional mages will have the largest collection of spells to draw from, including options for restoring strength if stoneflower petals aren't nearby. Sleep of the Old Hag is a disabling spell that blinds, drains agility, and drains fatigue from your enemies, while summoning upon them three Twilights for a short time. Rarely killing your enemy, instead it will haunt them and make them fall down in combat and miss their attacks more. Whether you follow with melee or magic, they will be much less effective. This birthsign is essentially weak to everything, so be careful with the Altmer race, making you extra weak to fire, frost, lightning, and magic.

FLOOD OF AMIBITION - DAGON
OBLIVIONWALKER (ability) Nerfs: weakness to shock 250%, weakness to frost 125%, mercantile and speechcraft are drained 15 points. Buffs: maximum magicka increased by 1.2, resist fire 50%, jump 5 points, athletics and speed 25 points.
INSTILL HOPE (major power) all for 30 seconds on self: light, fortify personality, speech and mercantile, drain fatigue 1-10 points
TOUCH OF DESTRUCTION (minor power) disintegrate weapon and armor 25-100 points each. Costs willpower to use.
MYTHICAL DAWN AMBUSH (minor power) bound axe, shield, curiass, helm, boots, and gloves on self for 120 seconds. Costs personality to use.
PLAYSTYLES: the ability to conjure weapons and armor on demand allows even a healer to have a formidable, dependable attack. The magicka boost is useful for many spellcasting classes. Speed is boosted which is useful on any playstyle. Dagon worship is a tricky business, with many summonings going bad for everybody involved. A scout for the Mythic Dawn would be a possible background. The Instill Hope power pairs well with the Bard class, making sure everyone can see the performance. Barbarians would appreciate the easy bound armaments and boost to speed. Watch out for jealous Frost and Storm atronachs.

MADNESS OF SHEOGORATH
EARWORM (ability) Nerfs: weakness to shock 500%, sound 25 points. Buffs: maximum magicka multiplied by 1.5.
MANIA (major power) all for 240 seconds: jump 50 points, slowfall 1 point, fortify speed 50 points.
RANT OF MADNESS (minor power) all for 30 seconds: drain intelligence 25-50 points on self, calm humanoid and calm creature 25 points on target, Costs willpower to use.
PLAYSTYLES: mages and spellcasters benefit from more magicka. Anybody that wishes to avoid violence could calm their enemies at will Rant of Madness. Thief builds could use the Rant while stealing everything that isn't nailed down. Mania is a fantastic way to travel. Sheogorath is the patron lord of madness, so the crazier the build, the better. The crippling weakness to lightning will make you fear certain situations. Crazed Sheo-worshippers have been known to go running in terror to shelter. Rant of Madness will drain intelligence and damage willpower, so the Breton's resistance to magicka is highly desirable, and they get a bit of extra magicka. Keep in mind Earworm will reduce your casting ability by 25%, especially hurting pure magic characters. For this reason, a warrior or thief-type could use Rant of Madness as a once in a while powerful calm spell with little penalty.
Recommended mods: the mod Lightning Strike is highly recommended for this birthsign! You are given a ring with this mod that configures how often lightning strikes and how much damage it does.

MARK OF HIRCINE
BLOOD OF THE HUNT (ability) Nerfs: weakness to fire 125%, weakness to normal weapons 75%. Buffs: restore health and stamina 2 points per second, detect animal 200 ft.
CALL OF NATURE (minor power) on self for 60 seconds chameleon on self 1-100 points, on target for 120 seconds light 10-60 points, weakness to normal weapons 50-100%. Costs speed to use.
PLAYSTYLES: Hircine hunts for sport, and likes to give his prey a chance to survive, even if remote. This is a hack-and-slash playstyle, with a minor power that marks the prey and makes them susceptible to unenchanted weapons, while garnering you near invisible. Alchemy or Restoration are highly recommended as major or minor skills so that your speed can be repaired as needed. Archer, Pilgrim, Knight, and Bard all have one as a major skill. Archer seems like a natural fit. Although the Reachmen could be a distinct race, they are related to Nords and Bretons, so these races could be natural followers of Hircine. Another idea is a "Wildcat" build:  a Hircine-marked Khajhiit Scout or Barbarian, who self-medicates with skooma and moon sugar.

MORA'S MINDBLOOM
FORBIDDEN KNOWLEDGE (ability) Nerfs: stunted magicka, weakness to magicka 500%, drain initial willpower stat by 25 points. Buffs: fortify maximum magicka x 1.7, spell absorption 85 points, detect enchantment 200 ft.
WELL OF APOCRYPHA (major power) all on self for 120 seconds: sound 1-100 points, fire&frost&lightning shield 20-40 points each, spell absorption 100 points, for 240 seconds: restore magicka 2-4 points.
BATTLESONG OF ZURIN (minor power) all for 90 seconds on self: sanctuary 50-90 points, weakness to magicka and fire 100-250% each. Costs strength to use.
SOUL RIP (minor power) all on target for 60 seconds: absorb magicka 5-15 points, soultrap, damage health 1-15 points. Costs intelligence to use.
PLAYSTYLES: Thematically sorcerers make great fits for Mora, being greedy for knowledge fits their profile. The crippling weakness to magicka will amplify many different spells, making this a difficult playthrough. Time can be spent collecting artifacts and spells that reduce the weakness, and this will lead to better utilization of their major power Well of Apocrypha. The secrets of the Telvanni may be worth uncovering for those following Mora. The minor powers are difficult to use, and your attributes will be severely damaged with the large weakness to magicka. However, Soul Rip gives you a long range attack that will be useful when using the Well of Apocrypha. The large spell absorption can make it difficult to restore attributes at shrines, so joining Imperial and native religions is recommended, for the cheap shrine usage, along with restoration and a good restore intelligence spell.

NAMIRA'S ROTTED SHADOW
NAMIRAS ROTTED SHADOW (ability) Nerfs: permanent -15 drain to Mercantile and Speechcraft, and start the game with -15 drain Personality. Buffs: 35% reflect spells.
FRENZIED FEEDING (minor power) all for 30 seconds on touch: frenzy humanoid 25 points, frenzy creature 25 points, absorb magicka and health 1-5 points, absorb fatigue 1 point. Costs personality to use.
NAMIRAS SHROUD (minor power) on target for 45 seconds: blind 50-100 points.
PLAYSTYLES: Namira is one of the gods worshiped in the Reach, so Nords and Bretons might be a good fit. The dro-m'Athra are Khajiit who have been corrupted by Namira, and thus would be a possible playthrough idea for this birthsign. Personality can be restored relatively easily, so alchemy and restoration are not critical, and going through the game with low personality can be sometimes entertaining. Frenzied Feeding can restore magicka, health, and stamina, useful for all classes. One tactic is to use frenzied feeding and then run away or hide from the enemy, while they slowly die and heal you. A former witchhunter or crusader that now champions for Namira would be a twisted take on these classes.

NEGLEGENCE OF NOCTURNAL
ESSENSE OF THE VOID (ability) Nerf: sun damage 1 point. Buffs: restore magicka 1 point, fortify sneak 20 points, fortify security 20 points, detect key 200 ft.
DAYWALKER (major power) all for 120 seconds on self: chameleon 25-75%, restore health 3-6 points, fortify speed 75-125 points, blind 25-50%.
SHADOWBIRTH (major power) all on self for 480 seconds: sound 10-35, blind 25-50, restore magicka 1 point, weakness to common disease 125-250%. Summon Winged Twilight on self for 60 seconds. On target for 30 seconds: shock and frost damage 20 points each. Costs endurance to use.
VOIDSHATTER (minor power) open lock 50-100 points, weakness to magicka 100% for 60 seconds, blind 40-50% for 10 seconds on self. Costs willpower to use.
PLAYSTYLES: sun damage is a crippling weakness. Darkness will be your friend, so prepare for a moody playthrough. Magicka will regenerate naturally at 1 point per second. You will have several option for locks with the boost to security and Voidshatter. The Nightblade class seems especially fitting, but any type of spellcaster will rejoice at their near constant full magicka bar. The major power can help you get to safe shelter when out in the sun, and also doubles as a defensive buff. A vampire playthrough might consider this birthsign, they would be powerful indeed until they felt even a hint of daylight. The major power Shadowbirth gives additional magicka regeneration, but at a nightmarish cost: a shadow born into the world, and your character is weaker from the experience.

PLAGUE OF PERYITE
PLAGUEBEARER (ability) Nerfs: weakness to cold 125%, weakness to magicka 75%. Buffs: restore magicka 1 point, resist poison 50%, resist disease 50%.
TOXIC BREATH (minor power) for 180 seconds on target: poison damage 1-8 points. Costs personality to use.
WASTING DISEASE (minor power) for 180 seconds on touch: poison damage 2-10 points, damage strength 1-3 points, damage speed 2-5 points. Costs personality to use.
PLAYSTYLES: a fire-and-forget playstyle, this character can spew toxic waste upon Vvardenfell with only personality to regret, which is relatively easy to restore. Spellcasters could obviously use the regenerating magicka, but the Peryite spells do not count towards destruction skill progress. Combat or thief types might enjoy the free access to powerful poison spells. In particular, the Rogue class would benefit from a ranged attack and a crippling touch spell, both unavailable to them otherwise.

RADIANCE OF MIRIDIA
GLISTWARD (ability) Nerfs: weakness to normal weapons 500%. Buffs: light 8 points, resist magicka 25%.
PATH OF BRILLIANCE (major power) all on self for 120 seconds: light 100 points, levitation 100 points, fortify speed 100 points.
PURIFICATION CEREMONY (major power) on self for 120 seconds: fire shield 30-70 points. On target for 60 seconds: weakness to fire 50-100%, fire damage 5-20 points.
TAKE COMMAND (minor power) for 60 seconds on target: turn undead 25 points, command humanoid 25 points. Costs personality to use.
PLAYSTYLES: Miridia is the Lady of Light, and attracts do-gooders, priests, and crusaders to her side. Crusader is an especially keen fit. Some see her as a champion of righteousness and an enemy of the undead. Others see her as manipulative, unyielding, even uncaring. The crippling weakness to normal weapons will make bandit caves a dangerous place. Overworld monster attacks count as normal weapons, but hand-to-hand fists to do not. 

VILE MEMORIES OF REGRET - CLAVICUS VILE
BINDING OF VILE (ability) Nerfs: weakness to poison 125%, weakness to normal weapons 75%. Start the game with personality damage 15 points. Buffs: fortify mercantile 50 points, fortify luck 25 points.
KEY OF CLAVICUS (minor power) open 50-100 points, for 45 seconds on self: weakness to magicka 125%, blind 25-75%, silence. For 10 seconds on self: paralyze. Costs speed to use.
EXCHANGE WARES (minor power) disintegrate armor and weapon on self 25-100 each. On self for 120 seconds: bound dagger, mace and longsword. Costs luck to use.
PLAYSTYLES: luck can benefit every skill, and every playstyle. The Key of Clavicus has many downsides, but gives cheap access to expert locks. Bretons, with a natural resistance to magicka, may utilize the Key with less downside. Eventually, a spell could be prepared that buffs magic resistance before using the Key. Classes without security or alteration may be an exceptional choice for this birthsign: Warrior, Crusader, Knight, Rogue, Bard, Archer, Barbarian, Monk, Pilgrim, and Witchhunter all need a way of opening tough locks. Speed is a difficult attribute to restore, so alchemy or restoration is recommended as a major or minor skill. In addition, the trio of bound weapons is useful to those skilled with them. That leaves Crusader, Bard, or Archer as recommended fits for this birthsign. The boost to Mercantile is significant, leading to cheaper travel, more money for training, and more bargaining power.

WEBSPUN HEART - MEPHALA
WHISPERED SECRETS (ability) Nerfs: weakness to fire, frost and shock 75% each. Buffs: willpower (25), hand-to-hand (35), speechcraft (35).
HIDDEN INTENTIONS (major power) on self for 360 seconds: chameleon 50%, bound spear, longbow, helm, boot, gloves, and cuirass.
GAZE OF TRUST (minor power) on touch for 30 seconds: charm 50 points, rally humanoid 25 points, rally humanoid 20 points, calm creature 25 points, rally creature 20 points. Costs endurance to use.
KISS OF THE WEBSPINNER (minor power) on target for 60 seconds: weakness to poison. on target for 20 seconds: absorb magicka 10-20 points. On self for 1 second: damage fatigue 200 points. Costs willpower to use.
PLAYSTYLES: Mephala worshipers are a great fit for the Morag Tong. Assassin is the classic fit, though even a healer can be dangerous with full bound weaponry and chameleon. This character will have a myriad of tools to manipulate those around them. Assassins also have alchemy as a minor skill, helping them craft potions to restore endurance. Other possibilities are agent, acrobat, and thief.

THE LAST TWO DAEDRIC BIRTHSIGNS
These last birthsigns were designed with the intention of being the ultimate challenge: they both have crippling damage weaknesses to common elements, multiple small secondary weaknesses, multiple powers with varying damage attribute costs, and both have a unique mechanic that offers an even greater challenge. Azura's birthsign constantly damages magicka, and Molag Bal's constantly damages strength. They both have powers that allow them to circumnavigate this challenge, however.
For RP purposes, the reason for these weaknesses could be that the dedication ceremony to these princes was stopped short by Priests. It could be also that the vanity of Azura or the maleficence of Bal made them turn their back to the character. Perhaps the cultists that performed the ceremony botched something up, saying the chant in Cyrodilli instead of Aldmeri.
Whatever the reason, your character is left nearly broken with weaknesses. Only by great determination will they persevere, maybe someday meeting the daedric prince they were promised to.

ORPHAN OF TWILIGHT - AZURA
DIMNESS OF SPIRIT (ability) Nerfs: weakness to common disease 50%, weakness to normal weapons 50%, damage magicka 1 point. Buff: chameleon 20%.
EBBING OF EVENING (ability) Nerfs: weakness to frost 500%, weakness to magicka 50%. Buffs: nighteye 30 points, fortify skill acrobatics 100.
DECLINE OF RADIANCE (ability) Nerf: drain skill Mysticism by 15 points, blind on self 8 points.
AFTERGLOW APLENTY (minor power) all on self for 5 seconds: light 5 points, fortify maximum magicka x3, fortify magicka 100 points. Costs agility to use.
SUNSET OF MAJESTY (minor power) on self for 30 seconds: lightning shield 30 points, fortify attribute luck 50 points. On target for 10 seconds: fire and shock damage 4-8 points each, invisibility. Costs luck to use.
DUSKS FINAL TWILIGHT (major power) on self for 240 seconds: lightning shield 70 points, chameleon 75, jump 10 points, fortify attribute speed 50, slowfall 5 points, blind 10 points, summon winged twilight. Costs speed to use.
PLAYSTYLES: magic will be difficult to use: the power Afterglow Aplenty will give you magicka for a very short time, so hot-keying this power is suggested, along with any other spells you might need to cast. Alchemy and/or restoration are highly recommended because you will have a variety of attributes to restore. Knight or Crusader would be excellent class choices because they have melee skills. Pilgrim and Witchhunter would be effective at range. On the other hand, a Breton or Altmer mage could be attempted, although the inconvenience and unreliability of getting magicka from Afterglow Aplenty would be tremendous. Luck influences potion and enchantment creation, so Sunset of Majesty could be used to aid these skills.
Sunset of Majesty grants a cheap ranged spell, and a protective lightning shield, all in one. It will render an enemy invisible, so beware if the enemy is strong. Afterglow Aplenty gives you a short-time well of magicka to use, possibly boosted if you can drink a quick-acting restore magicka potion in time. Agility can be easily restored looting the urns of tombs, and must be managed or you will fall down constantly.  Dusks Final Twilight is a swiss-army knife power, granting a powerful summon, lightning shield, chameleon, jump, and fortifying speed. The cost is speed, which will render you unable to move at all if it drops to zero. This long-lasting power could be used in combat or travel.
Acrobatics is boosted by one hundred points, which besides the nice boost also means that you are locked into this skill level for the whole playthrough. Since the acrobatics skill over 124 has the advantage of negating fall damage, it is recommended that you try to have at least 125 at character generation. This can be achieved if you take acrobatics as a major, although this reduces the number of skills that lead to level-ups. Additionally, the Khaajiit race would be an excellent choice to maximize this skill, with their racial boost to acrobatics, not to mention their lore-friendly connection to Azura. Khaajiit also would double up on the night-eye ability, granting them unparallel night vision. There are several artifacts and items that boost acrobatics, so achieving 125 is possible late game if you missed out: Surefeet, Marara's Ring, and others.
Factions to seek out would be: House Redoran, the dissident priests (not joinable), the ashlander tribes, all which share traditional Dunmer beliefs like Azura worship.

MALEFICENCE OF MOLAG BAL
PETTY DEPRAVITY (ability) Nerfs: weakness to fire 500%, weakness to shock 50%, weakness to normal weapons 50%, weakness to magicka 50%, drain skill restoration 15 points. Buffs: fortify athletics 100. Neutral: soultrap on self (RP reasons).
LESSER LAMENTATION (ability) Nerfs: damage attribute strength 1 point, burden 50 points. Buffs: fortify health 50, fortify maximum magica x1.5.
COMMON CARNALITY (minor power) on self for 5 seconds: fortify strength 50 points. On touch for 5 seconds: calm creature and humanoid 25 points each. Costs agility to use.
GREATER CURRUPTION (minor power) on self for 20 seconds: fortify agility 50, burden 25 points. On self for 60 seconds: fortify health 50 points, frost shield 30 points. Costs strength to use.
GRAND DEBASEMENT (minor power) on touch for 60 seconds: demoralize humanoid and creature 20 points each, burden 75 points, drain agility 50. On touch for 2 seconds: paralyze. On self for 60 seconds: fortify attribute strength 50 points. Costs endurance to use.
BLACK MALEFICENCE (major power) on self for 60 seconds: fortify blunt 50, frost shield 70, blind 25 points. On touch for 5 seconds: damage health 5-20, damage fatigue 5-20, absorb magicka 1-10. On touch for 60 seconds: frenzy creature and humanoid 25 points each, blind 25 points. Costs luck to use. 20 ft AOE radius.
PLAYSTYLES: with your strength being absorbed into Coldharbor constantly, you must rely on the gifts of Bal to pump up your muscles: Common Carnality for some quick juice, and Grand Debasement for a longer stream of strength. Light or medium armor is essential. Bound weapons have no weight, garnering them extra usefulness. Travel light.
Alchemy is highly recommended, especially since restoration is drained. You will have a multitude of attributes to restore, with endurance being the most critical. Bard and Witchhunter are the only classses with an alchemy major, but Battlemage, Scout, and Spellsword have it as a minor and should be considered. Agility or magic builds would have advantages from these powers as well.
Greater corruption can be used with impunity, since this is a strength-challenged build. Common carnality will give you a five second window to attack your calmed opponent, and the agility cost can be healed from bonemeal, a common ingredient. Grand debasement will demoralize and drain agility of your opponent, allowing you to knock them down more easily. Black Maleficence is a once-a-day AOE nuke power, hurting your enemies and stealing their souls for Bal. If used in a crowd, it can absorb large amounts of magicka.
The huge boost to athletics means that you are locked into whatever skill level you have at character generation. However, you don't need athletics as a major or minor skill for any reason other than more speed, and it will not advance your level-ups like another skill. If attempting to maximize this skill, the Argonian race paired with an athletics major would start the game with an incredible athletics stat.
These factions could be appealing to one marked by Bal: the Morag Tong, Telvanni, any of the vampire clans. Quarra is an excellent fit for their love of brute force.