I'm a bit new with animating dead, so bear with me.
I have to explain to my dm that you can create greater than 1HD undead with animate dead. He read the spell and dosen't seem to understand how it works.
Can anyone point me to the specifics on this? I'm not sure how best to prove that you can.
On a related note can only create basic skeletons or zombies, but can they be more than 1 HD?
Yes. Skeleton and zombie are both templates. Zombies also gain bonus hit dice based on their size, making them cost more if they're bigger.
As a fifth level caster, you can create up to 10 hit dice of undead with a single casting, but multiple castings would allow you to control up to 20 hit dice of undead.
Now, the fifth level caster just lucked out and killed a manticore. He decided to raise it as a zombie. A manticore has 6 racial HD and is Large, bringing its total up to an 8 HD dice zombie.
All you are doing is applying the Skeleton or Zombie template. So you couldn't create a 5 HD skeleton from a level 1 commoner's corpse - or any human, because they don't have racial hit die. But like in the manticore example mentioned above, you find something with racial hit dice and then those are used to calculate hit dice cost.
Prime example: if it couldn't create more than one hit dice at a time, large zombies would not exist, as large zombies have +2 HD over the base creature.
it depends on the type of creature. A creature that gets turned into a zombie loses all of its HD from class levels, so if you turn a Level-20 human Fighter into a zombie, he is not a 20 hd zombie, he is a 1 hd zombie.
You can make more powerful zombies by using a corpse of something that is more powerful. A basic Dragon, for example, does not have class HD, so it keeps its racial HD when you calculate its abilities as it turns into a zombie.
Check the Animate Dead spell and the rules for "Creating a zombie" in the bestiary. They are pretty well spelled out.