If a Graveknight uses its Undead Mastery ability:
As a standard action, a graveknight can attempt to bend any undead creature within 50 feet to its will. The targeted undead must succeed at a Will save or fall under the graveknight's control. This control is permanent for unintelligent undead; an undead with an Intelligence score is allowed an additional save every day to break free from the graveknight's control. A creature that successfully saves cannot be affected again by the same graveknight's undead mastery for 24 hours. A graveknight can control 5 Hit Dice of undead creatures for every Hit Die it has. If the graveknight exceeds this number, the excess from earlier uses of the ability becomes uncontrolled, as per animate dead.
Does it create a separate pool of controlled undead as opposed to the regular pool a caster would have? I assume the answer would be no, but the Undead Mastery ability is a (Su) ability and not a (Sp) ability which kinda flummoxes (wow when do you ever get to say that word in a sentence) my entire line of thinking.
It's a seperate pool. A graveknight cleric 10th would have both his 4xCL=40 HD pool from cleric, and his 5xHD=50 HD pool from the graveknight ability. For a total of 90 HD.
EDIT: Note:
The caster level based pool is (to my knowledge) nowhere to be found in the rules, outside of the animate dead spell, which I have always considered a reminder text. If anybody has a book and page number, I would appreciate it. Sorry for the hijack.
Thanks Don! Hopefully someone will answer your question with this bump, as I haven't a clue. I always just figured the rule was under Animate Dead as it is with many spells.