Revenant

Appearing much as they did in life, revenants returned from the world beyond the veil to complete some unfinished task—often taking revenge or solving a mystery. They do not know who they were or their life, but they have some clue on which to uncover who they were. They are aware of what they are and their purpose, but their reactions to that purpose depends on the individual

Sunlight & Animal Forms

Revenants appear as normal, living humans as they did in life but must hide their undead natures from sunlight by taking a crow, rat, or pike’s form. They may shift between these four forms, but if exposed to sunlight in human form, they immediately take 1d4 damage and an additional 1d6 for each subsequent turn of exposure. In beast form, they cannot speak or use weapons or equipment but are immune to the sun. While retaining their human form’s mental capabilities, saving throws, and HD, their beast forms have:

AC [12], ATT 1 x bite or claws (as unarmed), Movement: (130') Fly as a Raven, 60' (20') as a Rat, 150' (50') Swim as a Fish.

Undead

While Revenants can appear to eat, drink, and sleep as normal humans, they do not benefit. They cannot heal with rest or healing magic. Instead, at sunset and sunrise, they reroll their HD to determine their new HP total.

Undying

Until the mystery of their death and curse are solved, at 0 HP, Revenants fall. Unless the body is burned, dissolved, or otherwise disintegrated, it vanishes next sunrise, reappearing on or near their old tomb the following sunset. When they do so, they’re reduced to their current level’s minimum XP.
After resolving the task binding them to the mortal plane, they die normally at 0 HP and cannot be brought back by known magic.