Now of course shoot me down if this is a stupid idea, too time consuming or other constraints but I think it would be cool if there was an in-game bestiary, perhaps detailing monster information, any lore tied to the game or background meaning to the creature name.
Information like level range, elemental affinity, weaknesses, what species and family they belong to and how many times you've killed them. I would believe it could potentially be able to tie into RoE as well.