Eldritch Evolution

You magically consume the triggering creature's corpse and life energy, and turn it into new and burgeoning life. The triggering creature is magically buried in the ground and, in its place, a new creature appears. The new creature is a creature of your choice, with a challenge rating equal to 1 + the triggering creature's challenge rating. It is hostile to all creatures, no matter its alignment, as it is confused and its mind is fueled by primal rage. 

As an action on a subsequent turn, you can foce the new creature to make a Wisdom saving throw. On a failed save, it is friendly to you, though it doesn't obey your orders and it is not friendly to your companions.