I didn't have the patience to read the LN, but from what minor spoilers i've seen, she's one of, if not THE strongest in Nazarick after Ainz, and she gives him some REAL trouble, so it'll be the first time we see Ainz go ALL OUT, and our first glimpse at a really max level battle. Apparently its because she is a very well-balanced character, high HP, with resistances across the board, a natural life-drain ability and access to high level magic, plus several god items, while Ainz, in fact, is NOT optimized for combat, but is in fact built as more of a roleplaying character, with all his classes having been chosen to fit with the overall theme of an Elder Lich Master of Death and the Undead. Because of the way classes work in Yggdrasil, this particular combination of clases unlocked a special class for him that fits the theme, and as of yet unknown abilities regarding Death/Undead, plus giving him an insane amount of mana, much more than the ordinary max for a max lvl character, but left his stats poorly distributed in comparison to others, as he's TOO focused on magic. Interestingly enough, it seems that Albedo is NOT the strongest NPC, despite being chief. There seems to be some "surprises" left in Nazarick from the previous members too. All in all, i'm going to be VERY disappointed if there isn't a second series after this one, because there's POTENTIAL in this series, and a LOT of things yet to be discussed. I'm hopeful because they're apparently leading up to some very unresolved plot points that would end the series in a cliffhanger after the final episode, but, i've learned that i shouldn't get my hopes up after several discontinued animes...