Delving into the mysteries of Undeath, you are able to achieve more exotic results than mere dabblers in the Necromantic Arts. Using the Animate Dead and Create Undead spells, you are able to raise non-human zombies and skeletons, and exotic undead respectively. 

Using a series of Animate Dead spells, you can raise Zombies and Zombie like creations and Skeletal and Skeleton-like creations. You must cast Animate dead enough times that the CR of your creation is equal to the number of standard zombies you could raise, times four. Thus an Ogre Zombie (CR 2) requires 8 zombies worth of Animate dead to raise, and to maintain control of.

Create Undead similarly can be used to raise more exotic creations, such as Shadows, ghosts, et cetera, by casting enough times to raise a number of ghouls such that their combined CR is larger than the CR of the undead. For example, a Shadow (CR 1/2) could be raised with a single ghouls worth of casts, but a Banshee (CR 4) would require 4 ghouls worth. 

Any requirements described in the creatures entry must also be met. (I.E. a Crawling Claw requires a murderer's hand, a Banshee would require the corpse of a selfish, evil elf, etc. )

All creatures created this way take at least one ghoul/zombies worth of castings to create and maintain control over. (A crawling Claw requires 1 zombie worth, even though it is CR 0 )

The Dungeon Master must approve all uses, and as always is the final arbiter of whether a particular undead can be created, and whether the requirements have been fulfilled.