Would a creature with both Regeneration and Diehard die of HP damage when their HP reaches -CON, as per Diehard, or be able to stay up and moving until they are both at -CON and their regeneration is negated? Could a sufficiently motivated creature with Regeneration and Diehard persist into multiple negative hundred HP or more?
Diehard wrote:
Diehard
Prerequisite: Endurance.
Benefit: When your hit point total is below 0, but you are not dead, you automatically stabilize. You do not need to make a Constitution check each round to avoid losing additional hit points. You may choose to act as if you were disabled, rather than dying. You must make this decision as soon as you are reduced to negative hit points (even if it isn't your turn). If you do not choose to act as if you were disabled, you immediately fall unconscious.
When using this feat, you are staggered. You can take a move action without further injuring yourself, but if you perform any standard action (or any other action deemed as strenuous, including some swift actions, such as casting a quickened spell) you take 1 point of damage after completing the act. If your negative hit points are equal to or greater than your Constitution score, you immediately die.
Normal: A character without this feat who is reduced to negative hit points is unconscious and dying.
Regeneration wrote:
Regeneration (Ex)
A creature with this ability is difficult to kill. Creatures with regeneration heal damage at a fixed rate, as with fast healing, but they cannot die as long as their regeneration is still functioning (although creatures with regeneration still fall unconscious when their hit points are below 0). Certain attack forms, typically fire and acid, cause a creature’s regeneration to stop functioning on the round following the attack. During this round, the creature does not heal any damage and can die normally. The creature's descriptive text describes the types of damage that cause the regeneration to cease functioning.
Attack forms that don’t deal hit point damage are not healed by regeneration. Regeneration also does not restore hit points lost from starvation, thirst, or suffocation. Regenerating creatures can regrow lost portions of their bodies and can reattach severed limbs or body parts if they are brought together within 1 hour of severing. Severed parts that are not reattached wither and die normally.
A creature must have a Constitution score to have the regeneration ability.
Format: regeneration 5 (fire, acid); Location: hp.
