Although you are still a living creature, your flesh is infused with necromantic energies that make you, in some ways, akin to the undead.
Benefit(s): Negative energy damage heals you rather than harms you, as if you were an undead creature.
Positive energy still heals you as well, but it is only half as effective. In addition, when you are healed by positive energy, you must make a successful DC 15 Fortitude save to avoid being sickened for 1d4 rounds.
Sandy Petersen’s Cthulhu Mythos, © 2017, Petersen Games; Authors: Sandy Petersen, Arthur Petersen, Ian Starcher.