Coldblood Walker (Hollow One Variant)

Coldblood Walkers were the reanimated corpses of humanoids who died from exposure to the cold. Certain gods sometimes created coldblood walkers to remind the living of the power and wrath of winter. When a coldblood walker was killed, its remains could not be reanimated once again.

Unusual Nature. You don't require air, food, drink, or sleep.

Freezing Transfusion. As a Bonus Action, you can target a number of creatures up to your Proficiency Bonus that are within 30 ft. By expending any number of your available Hit Dice, you can heal each targeted creature an amount equal to the result of the rolled Hit Dice. You cannot heal yourself with this ability, and you cannot use this ability if you have no remaining Hit Die. These Hit Die can only be restored on a Long Rest as usual. 

Hollow Ones are those who were resurrected by strange necromantic magic, brought back without their soul but still with a sense of self.

Ageless. You don't age, and effects that would cause you to age don't work on you.

Cling to Life. When you make a death saving throw and roll 16 or higher, you regain 1 hit point.

Revenance. You retain your creature type, yet you register as undead to spells and other effects that detect the presence of the undead creature type.