This is my first mod for BG3. For the technical details of the class, the level progressions are in the image gallery and there is a full description below of all of the Tactician's features. For flavor though, let's describe it this way:

The Tactician is the fighter who makes a plan on how to take down every single person they meet, just in case. This is the hyper-observant duelist who reads every look and movement for injuries, habits, weaknesses, and then makes the perfect combo to take advantage of all of them. This is the one with the uncanny gift to see every attack coming and react before it has even happened. This is the chess master who is always five moves ahead of their opponent. This is the vigilante that has dedicated their life to studying every style of martial combat so they can adapt their attacks to any situation.

Brawn helps, but it is the mind that will win every fight.

 Tactician Class Features
An Intelligence based martial class.
 Primary features:

•  More Reaction points and reaction opportunities.
•  Stances that can be swapped between, each one offering some benefit.
•  Gambit Points fuel their abilities. Points are limited but regenerate each round (unless in a Stance) or when hit by an attack.
•  Compatible with level 13+ mods. (Not required)
•  Compatible with 5eSpells. (Not required)
  

 Class Feature Descriptions
Canny Measures: Gain one additional Reaction Point to use this round. [Cost: 1 Bonus Action]
Tactical Teamwork: When a nearby ally makes an attack, you may grant a bonus to the attack equal to your Intelligence modifier. [Cost: 1 Reaction, 1 Gambit Point]
Intelligent Defense: When not wearing armor, add your Intelligence modifier to your AC. When wearing Light or Medium armor, add half your Intelligence modifier to your AC. [Passive]
Help: Same as standard Help. [Cost: 1 Bonus Action]

 Combat Stances:
Stances cost 1 Bonus Action and 1 Gambit Point to enter, but once in a stance, it does not cost a Gambit Point to activate (or reactivate) a stance. However, being in stances prevents your Gambit Points from automatically regenerating each round. Stances have a duration equal to your Intelligence Modifier (minimum 1) and do not require Concentration. Upon reaching level 10 and gaining Improved Stances, all stances are automatically upgraded.

• Centered Stance: +1 AC, and you may use a Reaction to reroll a failed saving throw.
  
  • Improved Centered Stance: While in this stance, you also gain the benefits of Evasion.
    
• Deceptive Stance: +1 to attack rolls, and successful strikes have a chance to inflict Dazed.
  
  • Improved Deceptive Stance: Bonus increases to +2 and the save DC increases by 4.
    
• Focused Stance: Reduce the number needed to crit by 1 per stack of Focused Eye, to a maximum of 5. If you crit, the stacks reset to 1. On a crit, add your Intelligence modifier to damage.
  
  • Improved Focused Stance: Critting reduces your Focused Eye stacks by 1 instead of resetting them.
    
• Mobile Stance: Increase your movement speed by 3m and Attacks of Opportunity against you have Disadvantage.
  
  • Improved Mobile Stance: You are unaffected by Difficult Terrain.
    
• Vengeful Stance: Deal 2 additional damage when you have Advantage on the attack. Additionally, when attacked you may use a reaction to cast True Strike on the attacker and potentially inflict Frightened.
  
  • Improved Vengeful Stance: Advantage damage bonus increases to 4, and your True Strike Revenge is not automatically removed on your first attack.
    

    

• Arcane Stance (Augur): You may cast spells using Gambit Points instead of spell slots.
  
  • Improved Arcane Stance: While you are concentrating on a spell, you automatically deal psychic damage to enemies that get too close.
    
• Discerning Stance (Sleuth): Enemies you attack gain 2 rounds of Studied (-1 to attack rolls for each round remaining). At 5 or more rounds, this becomes Solved (Off Balanced: Disadvantage on attacks, Advantage for incoming attacks. Ends when damaged).
  
  • Improved Discerning Stance: Increases to 3 rounds per attack, and when a Solved enemy is struck it refunds the action or bonus action used for the attack.
    
• Harbinger Stance (Warlord): Enemies within 3m have Disadvantage on Strength, Dexterity, and Constitution saves.
  
  • Improved Harbinger Stance: Enemies within 3m have Disadvantage on all saves.
    

Fighting Style: The Tactician has access to all Fighting Styles except Great Weapon Fighting
Extra Attack: Tacticians gain an extra attack at level 5 and another at level 13. [Passive]

 Skirmisher:
Skirmisher options are minor tricks and techniques gained from battlefield experience.

• Combat Endurance: If you have no temporary HP at the beginning of your turn, gain 2 temporary HP. [Passive]
• Focus Fire: You have advantage on ranged attacks against opponents with less than 50% HP. [Passive]
• Gear Attunement: Gain an extra stack of Lightning Charges, Heat, Wrath, Momentum, Force Conduit, and Arcane Acuity when you are granted stacks by your equipment. Can only happen once per turn per stack type. [Passive]
• Gladiator: Gain Advantage on attacks when 2 or more enemies are adjacent. [Passive]
• Grit: Once per Long Rest, you may remove Blindness, Restrained, and other impairments and become immune to them for 2 turns. [Cost: 1 Action and 2 Gambit Points]
• Precise Aim: If higher, use your Intelligence instead of Dexterity for ranged weapons. Gain the Cool Headed action to remove Threatened and penalties from close quarter ranged attacks. [Cost: 1 Bonus Action and 1 Gambit Point]
• Training Drills: Deal an additional 1d4 damage with all special weapon-granted attacks. [Passive]
  

Extra Reaction: Tacticians gain an extra Reaction Point at level 7 and another at level 17. [Passive]
Improved Stances: As noted previously, all Stances are automatically upgraded when this trait is obtained. [Passive]    
The Tough Get Going: This attack deals extra damage depending on how much health has been lost. [Cost: 1 Action, 3 Gambit Points]
Supreme Stances: At level 20, stances no longer block passive Gambit Point regeneration per round. [Passive]

 Warlord Feature Descriptions
Proficiencies: Warlords gain Proficiency with 2 Handed melee weapons.

 Warlord's Armory:
Gain an additional Weapon Action based on a general category of weapon. These cost 1 Action and 1 Gambit Point to use.

• Axes: Sunder Armor decreases the target's AC by 3 for two rounds.
  
  • Axes deal bonus damage to opponents that are prone, restrained, or otherwise unable to move. [Passive]
    
• Blades: Bladestorm attacks 3 times, dealing half damage each time and potentially inflicting Bleed.
  
  • Damage dice for blades cannot roll a 1. [Passive]
    
• Blunt: Pummel does 1d4 extra damage and may knock the target back.
  
  • Hits with Blunt weapons inflict one round of Reverberation. [Passive]
    
• Polearms: Fell Sweep hits an area with reduced damage like Cleave and also may knock the targets prone.
  
  • Wielding a polearm or staff grants +1 AC against melee attacks. Reaction strikes in Vigilant Stance deal more damage. [Passive]
    
• Swords and Spikes: Blinding Strike does 1d4 extra damage and may blind the target.
  
  • Critical hits with these weapons might inflict Hemorrhage, which reduces the target's Constitution by 2. [Passive]
    

Warlord's Kit: Once per turn when you equip a new item, the Action Point used is refunded.
Class Stance: Harbinger Stance (described above)
Stunts: When you make a successful attack with Disadvantage, you may spend a reaction to also inflict Hamstring, Prone, or Bleeding. [Cost: 1 Reaction and 1 Gambit Point]
Rote Techniques: Once per Long Rest, you may use Rote Techniques to regain the use of all Once Per Short Rest abilities. This has no affect on action resources like Ki Points. [Cost: 3 Gambit Points]
Brutal Critical: Roll one extra damage die when you crit. [Passive]

 Sleuth Feature Descriptions
Proficiencies: Sleuths become proficient with Longbows and Heavy Crossbows

 Urban Archer:
A Sleuth has two passive abilities that can be toggled to modify ranged weapon attacks. They cannot both be active at the same time.

• Calculated Shot: Increases attack range by 50% and doubles your Proficiency Bonus to hit. Adds 1 Gambit Point to the cost.
• Ballistic Force: Reduces attack range by 33%. Deals 1d4 bonus Force damage and knocks the target back. Adds 1 Gambit Point to the cost.
  

Class Stance: Discerning Stance (described above)

 Tactical Foresight:
Gain 1 specialized cantrip and an additional benefit applied to the ally you assist with Tactical Teamwork.

• Cautionary Foresight: Blade Ward [Cost: 1 Bonus Action and 1 Gambit Point. Can target allies.]
  
  • Tactical Teamwork also grants your ally resistance to Bludgeoning, Piercing, and Slashing damage for the next round.
    
• Bolstering Foresight: Guidance [Cost: 1 Bonus Action and 1 Gambit Point.]
  
  • Tactical Teamwork also grants your ally an extra Bonus Action for this turn.
    
• Motivating Foresight: Bless [Cost: 1 Bonus Action and 1 Gambit Point. Only allows 1 target.]
  
  • Tactical Teamwork also increases your ally's movement speed by 3m for two rounds.
    

Adamantine Insight: You ignore resistance to Bludgeoning, Piercing, and Slashing damage. [Passive]
See Invisibility: Once per Short Rest, you can cast See Invisibility on yourself. [Cost: 1 Action]
Expertise: Choose two skills to gain advantage on their checks.

 Augur Feature Descriptions
Spellcasting: An Augur can learn spells and cast them without the need to prepare them in advance. The spellcasting ability is Wisdom.
Class Stance: Arcane Stance (described above)
Disciplined Mind: While you are in any stance, increase your spell save DC by 1. [Passive]

 Prescience

• Pain: When struck by an attack, you can cast Psychic Rebuke on your attacker. This spell deals extra damage if you are in Vengeful Stance. [Cost: 1 Reaction and 1 Gambit Point]
• Space: You can cast Tactical Transposition to swap places with an ally. While you are in any stance, you cannot be moved against your will. [Cost: 1 Action and 1 Gambit Point]
• Vision: You can cast Daylight with Gambit Points. You cannot be Blinded.
• Vulnerability: Learn Chromatic Orb. When you deal elemental damage that your target is vulnerable to, you deal extra damage of that type.
• Time: You can cast Haste with Gambit Points. You gain a +3 bonus to Initiative, and you grant allies within 4m a +1 bonus to Initiative. [Only available at level 9 and after]
• Weave: You can cast Counterspell with Gambit Points. [Only available at level 9 and after]
  

Bonus Gambit Point: The Augur gains one additional Gambit Point.