If I drain a baddie's endurance...

[Horror Pigeon]

If I do that for 1 second then their max health goes down. So their current
health has to go down to match it. So.. what happens after 1 sec and their
endurance returns? Does their lost health return or must they heal it back?

[Wai]

The damage disappears once the drain spell ends — unless the target's health was reduced to zero, either by the Drain to Health or by other damage taken while the Drain effect was active, in which case the target dies.

If you are going for such a short spell length, you might be better to consider using absorb Health, even though it is more expensive. At least that way you get some benefit yourself. In my opinion, if you are going to Drain, skill or attribute you need at least a few seconds to make it viable. The idea is to kill the enemy so you need the effect to last long enough to assist you. I would, at the very least increase the drain length to 3 seconds giving you a chance to have the drain effect active throughout the fight. You know that it is more effective to have lower value spells for longer. ie: drain magnitute 9 for 1 second will cost you more magicka than drain magnitude 3 for 3 seconds.

[Dallas S]

Drain health is next to useless, drain endurance is 100% useless because it does nothing, it only affects HP on a level up.

[Valden21]

It wouldn't actually have ANY effect on their health, according to UESP, Endurance doesn't affect maximum HP, it affects starting HP and the HP gain when leveling up.
However, the target's Fatigue and all their Endurance-based skills will drop. But this is only temporary, because when the spell wears off, the damage goes away. Quite frankly, any Drain Attribute spell of one second is worthless because of how quickly it ends. Go for a Damage Attribute spell, instead; the effects of those are permanent, and they're cumulative.

[Heimdall313]

Endurance doesn't determine health for NPCs and Creatures, Draining it has no apparent effect. Now on you the player, it'll drop your Fatigue. Its only effects on health are for the Player, determining your Base HP (End*2) and Health gain at level up (floor(End / 10)).

Originally posted by Dallas S:

Drain health is next to useless, drain endurance is 100% useless because it does nothing, it only affects HP on a level up.

Drain Health is exceedingly powerful. Drain Health 100 pts for 1 sec will auto-kill anything under 100 HP, and is an inexpensive spell with low requirements (Apprentice).
At Adept Destruction, you can stack it with Weakness to Magicka 100% for 4 Secs and you have a spell that doubles in damage on every cast.
4 casts will kill nearly anything at level 45. 100, 200, 400, then 800 Health damage. The only survivors are foes with heavy Magic resists and stuff like Lich/Xivali that absorb/reflect spells.
Draining a target's Health to 0 for even 1 second kills them without actually inflicting direct damage. Drain Health spells with 2+ seconds of duration, yeah those aren't useful.

Originally posted by Valden21:

Go for a Damage Attribute spell, instead; the effects of those are permanent, and they're cumulative.

That's Morrowind. Damage Attribute isn't in any built-in spells, or available on the Spellmaking menu.

Drain Speed is extremely useful though. Drain Speed for 15-20 pts heavily cripples most Creatures. Skeleton Champions for example only have 15 Speed. NPCs, Clannfear, and Spider Daedra are some of the only creatures that can even move with a 20 point Speed drain.

[Johnny Casey]

Originally posted by Heimdall313:

Drain Speed is extremely useful though. Drain Speed for 15-20 pts heavily cripples most Creatures. Skeleton Champions for example only have 15 Speed. NPCs, Clannfear, and Spider Daedra are some of the only creatures that can even move with a 20 point Speed drain.

One thing I hate about draining enemy's speed to zero is that it stops the combat music. And if they're attacked while under the effect of drain speed, the combat music briefly starts the moment you strike and then stops again, and this goes on and on until either the effect wears off or they die.

It was bothering me so much so that I had to ditch the idea of draining their speed and have drain strength with burden instead to demobilize them, which costs more magicka. Story of my life.

[Heimdall313]

Originally posted by Johnny Casey:

Originally posted by Heimdall313:

Drain Speed is extremely useful though. Drain Speed for 15-20 pts heavily cripples most Creatures. Skeleton Champions for example only have 15 Speed. NPCs, Clannfear, and Spider Daedra are some of the only creatures that can even move with a 20 point Speed drain.

One thing I hate about draining enemy's speed to zero is that it stops the combat music. And if they're attacked while under the effect of drain speed, the combat music briefly starts the moment you strike and then stops again, and this goes on and on until either the effect wears off or they die.

It was bothering me so much so that I had to ditch the idea of draining their speed and have drain strength with burden instead to demobilize them, which costs more magicka. Story of my life.

Ha yeah its irritating. One sec of Paralyze will work too in most cases; Skeletons are immune but they get dunked by Drain Speed.
You can also use Drain Speed for 1 second on Touch and Invisibility on Self spell to just ghost something and leave.