Animate Familiar

This spell creates an undead familiar. You choose a pile of bones or corpse of a tiny beast such as a bat, cat, crab, frog (toad), hawk, lizard, octopus, owl, poisonous snake, fish (quipper), rat, raven, sea horse, spider, or weasel. The familiar has the statistics of the original creature but is an undead instead of a beast. The target is raised as a skeletal version if you chose bones or a zombified version if you chose a corpse. The familiar has immunity to poison damage and is unable to have the exhaustion condition or be poisoned.

The familiar acts like that of the familiar in the find familiar spell and has all the same stipulations and actions available with the exception of being able to dismiss your familiar. Instead of dismissing your familiar you may temporarily return it to death, in order to return your familiar to undeath you must be on the same plane as you and must not be on sanctified ground. If its on sanctified ground you know the exact location and state of your familiar.

Your familiar gains the following traits based on type:

Pile of Bones (Skeletal Familiar). As an action the familiar can turn into a pile of bones or back into it's original form. While a pile of bones, the familiar is indistinguishable from an ordinary pile of small bones, it's speed is reduced to 0, and it can only use it's action to transform back into it's animated form.

Undead Fortitude (Zombified Familiar). If damage reduces the familiar to 0 hit points, it must make a Constitution saving throw with a DC of 5 + the damage taken, unless the damage is radiant or from a critical hit. On a success, the zombie drops to 1 hit point instead.