Does this rule actually exist?

[Timely Drought]

Sorry for the hijack, but where is the -10 rule in 3.5? I didn't know about that one. My players would hack at regenerating creatues into the -50's to buy time until they could figure something out. This changes the scope of things immensely.

They'd not be dealing damage to hit points. Regeneration would convert most type of attacks to nonlethal damage, which is counted upwards and don't have a limit.

Regeneration does not protect against suffocation. Some DMs rule that decapition kills regenerating creatures but that books don't say if that should work or not. But even if you judge that regenerating creatures can breathe headless through their windpipes, you can just stick your dirty socks in the throat and wait for it to choke.

 

[Knight Otu]

Mouseferatu, I think your group subconsciously stole that rule from GURPS - remember the "Harry the Hamburger" sidebar example in the combat chapter of GURPS 3rd edition?

It certainly sounds like that rule.

-HT: Roll against original HT or die.
-5xHT: Dead
-10xHT: Finely chopped meat

Darklone - what rule are you referring to?

 

[Darklone]

Undead Type: Undead are once-living creatures animated by spiritual or supernatural forces.
Features: An undead creature has the following features.
—12-sided Hit Dice.
—Base attack bonus equal to 1/2 total Hit Dice (as wizard).
—Good Will saves.
—Skill points equal to (4 + Int modifier, minimum 1) per Hit Die, with quadruple skill points for the first Hit Die, if the undead creature has an Intelligence score. However, many undead are mindless and gain no skill points or feats.
Traits: An undead creature possesses the following traits (unless otherwise noted in a creature’s entry).
—No Constitution score.
—Darkvision out to 60 feet.
—Immunity to all mind-affecting effects (charms, compulsions, phantasms, patterns, and morale effects).
—Immunity to poison, sleep effects, paralysis, stunning, disease, and death effects.
—Not subject to critical hits, nonlethal damage, ability drain, or energy drain. Immune to damage to its physical ability scores (Strength, Dexterity, and Constitution), as well as to fatigue and exhaustion effects.
—Cannot heal damage on its own if it has no Intelligence score, although it can be healed. Negative energy (such as an inflict spell) can heal undead creatures. The fast healing special quality works regardless of the creature’s Intelligence score.
—Immunity to any effect that requires a Fortitude save (unless the effect also works on objects or is harmless).
—Uses its Charisma modifier for Concentration checks.
—Not at risk of death from massive damage, but when reduced to 0 hit points or less, it is immediately destroyed.
—Not affected by raise dead and reincarnate spells or abilities. Resurrection and true resurrection can affect undead creatures. These spells turn undead creatures back into the living creatures they were before becoming undead.
—Proficient with its natural weapons, all simple weapons, and any weapons mentioned in its entry.
—Proficient with whatever type of armor (light, medium, or heavy) it is described as wearing, as well as all lighter types. Undead not indicated as wearing armor are not proficient with armor. Undead are proficient with shields if they are proficient with any form of armor.
—Undead do not breathe, eat, or sleep.

 

[Knight Otu]

Yes, Undead (and Constructs, too) are destroyed at 0 or less hp. So you were answering Ahrimon? That's what I should have asked.

Ahrimon, apart from the bit about regenerating creatures suffering only subdual damage, you might check the Injury and Death section and the Condition Summary:

DEAD (–10 HIT POINTS OR LOWER)
When your character’s current hit points drop to –10 or lower, or if he takes massive damage (see above), he’s dead. A character can also die from taking ability damage or suffering an ability drain that reduces his Constitution to 0.

Dead: The character’s hit points are reduced to –10, his Constitution drops to 0, or he is killed outright by a spell or effect. The character’s soul leaves his body. Dead characters cannot benefit from normal or magical healing, but they can be restored to life via magic. A dead body decays normally unless magically preserved, but magic that restores a dead character to life also restores the body either to full health or to its condition at the time of death (depending on the spell or device). Either way, resurrected characters need not worry about rigor mortis, decomposition, and other conditions that affect dead bodies.

 

[The Souljourner]

It's a house rule, because, by RAW, you cannot reduce a living creature below -10 hp (which is why the tarrasque-slaying condition was changed in 3.5).

Umm.... no.

DEAD (–10 HIT POINTS OR LOWER)

When your character’s current hit points drop to –10 or lower, or if he takes massive damage (see above), he’s dead.

Please note the "or lower" in there.

The reason the Tarrasque's entry was changed is because you can never actually get it to negative hitpoints, since nothing does real damage to it, thus nothing reduces its hitpoints... it just accumulates non-lethal damage.

-The Souljourner