Depends! Usually you don't wanna use your own blood, because that tends to make pacts you really shouldn't be getting into. So usually it's best to use other animals.

...But you always ask their permission first! That's very important for the rituals, mhm.

[No it's not. Henry just doesn't like cutting open animals without consent.]

You know, you're really interested in this all of a sudden! Do you want to get into dark magic, or what?