You find yourself in the empty body of a skeleton, a corpse made of calcium and bone. Your consciousness is stored inside your head and so long as your skull is intact so shall you. You can change bodies so long as it is skeletal in nature. But your true power is your necrotic powers over the dead alike.
You can use corpses to create shambling loyal soldiers that do your bidding. The more powerful the corpse the more powerful the undead in question. A completely normal human body might find itself barely keeping together while the corpse of a powerful being possesses the powers it had in life and can move with fluidity. Although a significant strength difference might degrade the undead even more.