Undead Beast

This spell has the capability to bring a creature back as an undead creature. The creature keeps its memory and behavior you know and shared with it,
as long the creature gets brought back within 30 days. Exception: if the spell user has the feat Keen Mind.
If this doesn't happen within this timeframe the animal will start imitating the behavior of an average creature of its race.

The creature that can be summoned depends on the spell level. The spell allows you to to summon an CR 1/4 beast that you own the scull of.

The undead beast at the regular spell slot will be animated for 3 days.
Within these 3 days the caster is able to recast this spell to refresh the effect the time limit free of cost.
The creature can be dispelled retreating into its onyx and brought out. This doesn't stop the 3-day timer.

If the creature dies it will drop its skull.

At higher Levels:
You can summon a beast one iteration of CR higher starting of 1/4 with each level you spend.
Additionally using a spell slot of level 6 or higher will make the spell permanent.