So we've already had (via the wiki): evocation, illusion, conjuration, transmutation, divination, and whatever the animus bell is which has pretty much gotta be necromancy, right? So of the D&D schools of magic that are left over, there are two left that the final relic could be (assuming that this theory about them being all different schools is correct): enchantment or abjuration. So far we know of six, and according to something Griffin said near the beginning of the show, they're all from different schools of magic. Well, plus we know there's one more grand relic out there. Griffin has promised one more arc, and I believe we're going to get it. The liches have no connection to the greater story of the War and the Voidfish and the Black Cloud-we're nowhere close to resolving all of that.