Basically, I have a player who wants to use the improved familiar feat to get a Runic Guardian(mm2, P. 182) as his familiar. I've looked over every rulebook for all the scraps of info I could find, and I'm left puzzled. It suggests Level, size category, and even base attack bonus requirements, but doesn't ever seem to give any details about what those requirements are. Also, it seems like the rules between Complete Warrior and the DMG on improved familiars are in conflict. Can anyone please clarify this for me, and explain which book would be considered the source to follow?