Morph Adapter (3.5e Feat)
From D&D Wiki
Morph Adapter [Special]
Adaptable to tough situations
Prerequisite: Con 13, must be able to change shape in one of the following five ways: change shape supernatural ability, shapechanger subtype, polymorph as a spell-like ability, able to cast the polymorph spell, wild shape or similar class feature
Benefit: While resting (not taking actions), you heal nonlethal damage at a rate of 1 hit point per minute (including ones taken from hot/cold environments). You can also survive without water, food, or air as twice as long. You also recover from exhausted to fatigued in a minute, and from fatigued to normal in five minutes.
Normal: Nonlethal damage are healed 1 hit point per hour. Damage from hot environment cannot be healed unless you move into a cooler environment. Damage from cold environment cannot be healed unless you move into a warmer environment. You survive without water for a day + an hour per Constitution score before taking damage. You survive without food for 3 days before taking damage. You survive without air for 2 rounds per Constitution score before taking damage. It takes an hour to recover from exhausted to fatigued, and it takes 8 hours to recover from being fatigued.
Special: This feat can be taken up to 3 times. Each time you take the feat, you are healed 1 more hit point per minute, and the period you can survive is tripled and quadrupled, respectively. Recovery from exhausted and fatigued state does not change. If you cast the polymorph spell, has polymorph as a spell-like ability usable less often than at will, or has the wild shape class feature, then this feat loses function when you cannot use them.