This mod alters the properties of some magic effects through OBSE commands, reaching options that are unaccessible in the standard Construction Set. These options are typically the checkboxes that are greyed out in the magic effects window, like the ones specifying possible range for spells, or whether the effect has magnitude, area or duration.
Currently it gives new and more consistent counter effects to Fire, Frost and Shock damage; removes the unnecessary counter effect from Feather; makes Disintegrate Weapon and Armor show no duration in the spellmaking menu; and allows custom Absorb spells on target and Open spells on touch to be created.
As of version 3.0, it also allows you to easily change the Constant Effect Enchantment Factor of any effect to whatever you like, through an additional .ini file.
In version 3.2, you can also change the magnitudes of effects in particular magic items through yet another .ini file.
In version 4.0, you can edit the list of magic effects on any ingredient through yet another .ini file.
It also includes optional tweaks through the Oblivion Magic Extender to Dispel, Cure and Charm effects. OBME is not required for the mod to run, if you don't have it installed those tweaks will simply not be applied.
All these options are configurable under 'Data\Ini\Magic Effects OBSE Tweaks.ini', 'Data\Ini\Magic Effects OBSE Tweaks - CustomCEF.ini', 'Data\Ini\Magic Effects OBSE Tweaks - CustomMag.ini', 'Data\Ini\Magic Effects OBSE Tweaks - CustomING.ini', in case you don't want all of them active. You can even delete the ones you don't want to load, in case you want to do away completely with some of my changes, though I'd recommend you to go through them and comment in/out what you want/don't want, and edit them to your liking of course.

Note about Counter effects: most hostile magic effects have a counter effect list defined which you can see in the CS. These 'counter effects' are not necessarily the effects which will nullify that hostile effect, but rather, they are used by the Artificial Intelligence engine, so that when a NPC is under the effects of such a hostile effect, he will prioritize using the counter effects for that effect, searching for them in his available spells, potions and scrolls.
That is why all hostile effects have 'Dispel' as a counter effect: it is the most universal and reliable way of getting rid of an effect. Some effects have additional counter effects which the AI can try to use if it doesn't find any magic items with dispel.
The counter effects of an effect cannot be changed in the CS, but can be changed with OBSE, altering the way the AI will try to get rid of them.

Fire, Frost and Shock damage are given the same counter effects as the Damage Health effect in addition to their corresponding elemental shield and elemental resistance. This means the AI will now try to use absorb, fortify and restore health spells and items when affected by elemental damage spells, in addition to trying to dispel them or use the corresponding shield or resistance effects.
If using Supreme Magicka, its Poison Damage effect will also receive a Resist Poison counter effect which it previously lacked. Note that Cure Poison cannot affect Poison Damage, at least not yet.

Feather had the Dispel counter effect, which isn't needed since it is a beneficial magic effect, so it is removed.

Disintegrate Armor and Weapon have a bug that prevents the duration of any effects with them from working. All the magnitude that the Disintegrate effect lists is applied at the moment the spell impacts, and the effect does nothing else for the duration it lasts.This mod cannot fix this but keep reading:
Due to all effects from custom spells in the spellmaking altar having a minimum duration of 1 sec if the effect has duration, it is impossible to avoid creating Disintegrate spells with a minimum duration of 1 second, which does nothing for the spell. Therefore, duration for Disintegrate effects is disabled, so that you can create Disintegrate spells with no duration and waste no spell cost in spellmaking.

Demoralize and Frenzy can be set either or both to be hostile effects, for the AI to better handle them (in theory), though note it will also prevent most exploits you could do with these effects. It also allows you to brew poisons with these effects (like in Skyrim), but unfortunately there are no ingredients with these effects, though I have provided some examples to alter some vanilla ingredients to pack these effects in 'Data\Ini\Magic Effects OBSE Tweaks - CustomING.ini'

Absorb effects can now be made available on target, like in Morrowind. Absorb uses the fAbsorbDistanceReachMult game setting to determine the maximum distance at which they work (the distance at which the magic cord coming from the actor you absorb from breaks, ending the spell). This game setting is by default 3, which I believe is something like 5 meters. By default this mod sets it to 30, allowing absorb to have nearly unlimited range and making on target Absorb spells much more useful. (Note that the developers made Absorb on touch only likely for balance reasons, though absorbing from an enemy half a mile away and seeing how he dies running towards you may not be balanced but is quite fun)

Open can now be made available on touch, also like in Morrowind. Custom on touch Open spells can be made, which will work underwater and are notably cheaper than their on target counterparts. Again, it was probably done on target only for balance reasons, to not make the security skill entirely useless, but IMO security is already useless enough without this option.

The following have their own ini files to fine tune their features:
Custom Constant Effect Factors: you can define for each effect what should be its magnitude on a enchantment you make yourself with a grand soul in the file Magic Effects OBSE Tweaks - CustomCEF.ini. It also applies to all other soul gem sizes, so a petty soul makes an enchantment with 1/5 of the magnitude, a lesser one 2/5, etc.

Custom Magic Item Magnitudes: the file Magic Effects OBSE Tweaks - CustomMag.ini allows you to change the magnitudes of any particular effect found in magic items. By default, it contains all magic items containing any of the three Cure effects and adjust the magnitudes of these effects, in case the options below to alter the Cure effects through OBME are active, and you can define your own magic items to be altered in addition to those. An effect's magnitude will only be changed if the magic item contains that effect AND the effect doesn't have the 'No Magnitude' flag.

Custom Ingredient Effect lists: the file Magic Effects OBSE Tweaks - CustomING.ini allows you to alter the magic effects list of any ingredient, for them to have the effects you want and to appear in the order you want. By default some vanilla ingredients are provided with frenzy and demoralize effects, simulating the ones from Skyrim, and meant to allow brewing poisons with these effects if the option above to make these effects hostile is enabled.


Next come some OBME tweaks, these are optional and will not be applied if you don't have OBME installed. They will change the behavior of the Dispel effect, the three Cure (Disease, Paralysis, Poison) effects and the Charm effect to be quite more interesting:

Dispel will no longer be 'all or nothing', instead when you cast or use a Dispel effect, its magnitude will be distributed among all the active effects affecting you and reduce their duration proportionally. Using enough Dispel can get you rid of any effect, but weaker Dispel effects will need many applications to achieve this. Dispel can now also affect magic effects coming from weapons, staffs and scrolls, in addition to spells.

Cure Disease, Poison and Paralysis can now be changed to the Dispel handler. They will now have a magnitude which is proportional how much of the effects from diseases, poisons or paralysis affecting you will they remove.
This means that, if using the Cure Disease tweak for example, eating a Clannfear leg raw or any ingredient with Cure Disease as its first effect will no longer cure you of anything at all, you will have to brew it into a potion first, and even then you are likely to need many potions before the disease goes completely away, same for poison and paralysis. By default, the Magic Effects OBSE Tweaks - CustomMag.ini file has data set to apply a suitable magnitude to all vanilla spells and items using Cure effects so that you can use them, as well as to some spells from mods like bg's LAME magic overhaul and Race Balancing Project, with no requirements on them. Finally you can set a multiplier for the cost of these Cure effects so that magic items with them have a reasonable cost, the default and suggested value is 0.015, i.e. Cure Disease will go from 1400 to 21 base cost, and a 25pts magnitude spell will have a base cost of 129.
As and added bonus, Cure Poison now offsets any hostile effect from any potion, poison and ingredient affecting you, thus being useful for alchemists when wortcrafting ingredients or creating dangerous potions.

NOTE About Cure Disease: the tweak to Cure Disease is currently disabled by default in the ini, since even if the effects of the disease are removed, the disease itself stays on the player. Future versions of OBME will fix this, if OBME is ever updated.

Charm is actually nothing but a Fortify Personality effect, which means the raise in disposition was only a side effect of NPCs with higher personality having higher disposition towards every other actor, not just the player. If a mod changes the game settings that control how disposition is calculated, charm effects may not raise the disposition of the target by the amount that the effect claims.
With OBME, I have fixed charm to use its own scripted effect, that will raise the target's disposition towards the caster, and only towards the caster, by the amount specified in the effect always, after applying spell effectiveness modifiers.

The mod is and should be compatible with everything because it doesn't touch the magic effects directly, it changes them through a script once when the game starts, and nothing else.

To install, drop the contents in your Data folder. You can customize the options in 'Magic Effects OBSE Tweaks.ini' and associated .ini files, under the 'Data\Ini' folder. To uninstall, simply uncheck and/or delete 'Magic Effects OBSE Tweaks.esp' and those ini files, the changes to magic effects will not persist since they are restored to vanilla behavior at game startup.

Thanks go to the OBSE team for unlocking all the customization options of magic effects. IMO the only reason the vanilla CS didn't do that was to prevent us from messing things up, a.k.a to prevent us from having fun.
Thanks to JRoush and his OBME utility for allowing the impossible with it.

Enjoy