Necromancy. It is one of the Alternate World's normal classes and is said to be connected to the Goddess of Death. Although not sure whether it is true or not, the ability to control the dead to your bidding is something that is not just considered to be in the teachings of the goddess of life, but also quite frowned upon by many who believed the goddess of life.
I have gained a skill book related to the Necromancy class tree and it unlocks many stuff related to it that was not present in the original Necromancer tree. And one of them is retaining the summoned skeletons and any summoned ghouls and zombies at their disposal anytime they want and reusing them in any fight, allowing the summoned monsters to actually gain a level and get strong if they survived long enough.
