If you are familiar enough with these games, you may have noticed that temporary HP is handled differently in the Infinity Engine games than in AD&D.

AD&D temporary HP:
You gain an extra pool of hit points, which are separate from regular HP. When you take damage, it is subtracted from the temporary HP (tHP). This loss of tHP can't be healed through conventional healing. When the effect wears off, any remaining tHP go away along with it.

Infinity Engine temporary HP:
Your maximum HP increases by the amount (this effect is temporary), and you are then healed by that amount (this is permanent in the same sense that Cure Light Wounds is). Damage taken can be healed normally, up to your current higher max HP amount. When the effect wears off, your max HP returns to normal, but your current HP will only decrease to its normal maximum, even if it is higher than your HP just before the spell was cast.

One implication of this difference: in IE games, a spell that provides temporary HP will provide permanent healing. Hence, you can use Aid as a healing spell between battles. In AD&D, this doesn't work; the HP is lost when the spell ends.

By the way, does the BG2 implementation of Vampiric Touch, which doesn't let you use it for more HP until the first casting's duration runs out, bug anyone else? (I'd be inclined to mod that spell and either: 1. allow the HP to stack infinitely, or (if playing an Enhanced Edition) 2. make it so that each casting of the spell dispels the previous casting, causing you to lose the max HP (but not current HP) the previous casting gave you.) Does it bug you that casting Vampiric Touch makes you immune to damage from enemies casting that spell on you? (Do any enemies use that spell in the unmodded game?)

I find it really baffling why some people fail to acknowledge the difference between BG Infinity Engine rules and P&P rules. They are not the same, never were the same, and can never be the same. The train has come and long gone. Deal with it.

I am acknowledging that they are, indeed, different. (If you notice, I am actually pointing out one of the differences.) I am wondering how players *prefer* such things to work.

On the other hand, the BG2 behavior of Vampiric Touch has always bugged me since I encountered it; it seems that cRPG developers never get that spell right. In Dungeon Hack, for example, the spell did give you "temporary" hit points that were separate from your normal hit points (that much is accurate), but the hit points would stack without limit over multiple castings and would not wear off when you take damage (that isn't accurate and resulted in the spell being capable of breaking the game). (Aid at least was accurately implemented except for the duration, but the Dungeon Master like setup of the game makes the whole notion of duration different.)

As for other games:

The Gold Box games don't implement temporary hit points at all. If you notice, those games lack spells like Aid and Vampiric Touch.

The Dark Sun games seem to treat such effects as healing that is allowed to exceed your normal maximum, much like certain fountains in some Might and Magic games. I haven't played/tested the game enough to describe how it works exactly, but I noticed that the hit points from Aid don't seem to go away with time (see my topic on the Dark Sun forum).

Temple of Elemental Evil is close; it actually has a temporary HP effect that is decreased before regular damage is received and has a finite duration. However, False Life stacks over multiple castings (allowing Sorcerers with this spell to tank in a way they aren't meant to), and Vampiric Touch is broken in the sense that it doesn't work properly (it does give you a temporary HP effect, but that effect provides 0 temporary HP, which isn't helpful).

I haven't tested in Neverwinter Nights or its sequel, but the Wiki says Vampiric Touch gives temporary HP, but also erases any already present, even if they are from a different source. (This is probably the easiest and most clear way to implement the mechanic, even though it disallows certain things that the P&P game allows.)

I happen to like the temporary HP mechanic; it's just that developers of D&D cRPGs can never seem to get the mechanics right.

That's because computer games are not P&P games. *Sigh!*

Here's an interesting question: Do you like the fact that spells like Aid and Vampiric Touch can be used to grant permanent healing (as in IE or Dark Sun cRPGs), or would you prefer it if they solely act as damage prevention (as in P&P)?

Also of note, I have noticed that the developers of fix packs and similar mods seem to be of the notion that spells should behave as in P&P rather than how they actually behave in the vanilla game. (Examples include making certain effects not stack with themselves when they do in vanilla.)

I finally used Vampiric Touch in the current playthrough. Had always assumed it was a bit cack, so was gobsmacked by how powerful it was. For instance ~doubling HP from around 60 to 130. If it was possible to stack these spells, it would be so OP to be laughable. Do that with a fighter-mage, and good grief...

Looks like the issue with Baldur's Gate, for you, is the lack of ways to cheat the game. Shocking, I know, but some of us just like to play the darn thing.

Yeah, and they are just fans, much like most of the developers of the Enhanced editions -- most of the 'additions' come from mods. Their interpretations are not what the original developers intended; the developers developed a unique system, and that system is what makes the game.

Actually, my understanding is that it is not supposed to be *that* powerful, but occasionally is due to a bug. Normally, it is only supposed to give 6d6 (or average 21) HP at most. (Does anyone know what triggers this bug?)

Thing is, the current way of handling it makes regular use of Vampiric Touch impractical, as it basically can only be used once between rests.

The way the spell works in P&P (to my understanding) is that you cast the spell to get some temporary hit points, have the tHP shield you from some real damage, and then cast the spell if you need more later. If you try this in BG2, the Vampiric Touch spell will fail, even if you have already lost the hit points gained, unless the duration has run out.

Incidentally, there is a similar issue with Project Image in IWD:EE. If the spell's duration has not worn off and the caster hasn't been hit with a dispel, you can't create another image even if the first one has been dispelled. (I see this as an unintended side effect of an exploit patch.)

It's only an issue in BG2, where randomness comes into the equation -- it does not in BG1. No. It can be used at any time after the original has worn off (300 seconds). The spell itself (BG2) has a 'protection from Vampiric Touch' element.

Thing is, 5 minutes is quite a while to wait after one casting if I don't want to rest, and it is unlikely to happen during the same battle.

I did think of a third way of making the spell suit my tastes better: Make it so that it provides healing rather than temporary hit points. (This appears to be the approach 5th edition took.)

Incidentally, in 2e AD&D (P&P), the behavior of the spell is actually closest to the behavior in the Dark Sun games:
"The hit points are added to the caster's total, with any hit points over the caster's normal total treated as temporary additional hit points."

In other words, the spell first heals the caster, and only then do the additional points become temporary hit points.

3.5e, on the other hand, made it provide only temporary hit points. Then 5e came along and made the spell provide only healing (and only half the damage as healing).

That's why moving on to the next battle will allow you to cast it again; you don't have to rest, other than to refresh your spells, which is something (rest spamming) I avoid like the plague. There's nothing that ruins my game quite like having to continually rest, which is why I have always wished it was a mana based system like DA:O, Drakensang et al.