Vampiric Familiar

Semi-Incorporeal Movement. The familiar can move through it's master space as if they were difficult terrain.

Shadow Mirage. The familiar can change it's form to one of an animal, it's master determines what animal it will change into it will mimick the movement style of that animal, using short range telekinesis(5ft, 200 lb limit) it can interact with it's surroundings, however it cannot directly cause harm to other creatures. 

Anyone that can see through illusions can see it's true form as a shadowy figure mimicking the size and shape of the animal it changed to.

Bounded Servitud. The familiar has no real free will, however when not given a direct order it will act on it's own if it's action will benefit it's master.

One with Shadows. When the familiar is in an area of dim light or darkness, they become invisible.

Giveth/Taketh Away. Should the familiar's master Hit Points reach below 1 the familiar teleports to it's master's space and fuse with them, The master gains half of the remaining hit points(round up) the familiar had and the familiar disappears until summoned again.