You have discovered ancient arcane secrets of necromancy that allow you to reanimate the corpses or bones of more powerful creatures. You gain the following benefits:

• You can raise undead Beasts by casting animate dead at 4th level.
• You can raise undead Monstrosities by casting animate dead at 5th level.
• You can raise undead Aberrations, Celestials, Fey, and Fiends by casting animate dead at 6th level. 
• You can raise undead Giants by casting animate dead at 7th level.
• You can raise undead Dragons by casting animate dead at 8th level.