The Elden Ring Ansbach quest follows the ex-servant of Mohg as he tries to work out exactly what's going on with Miquella in the Land of Shadow. This retired Pureblood Knight is a learned NPC who'll give you extra context and lore if you provide him with certain information, such as Miquella Cross locations early on in the Shadow of the Erdtree expansion.
Unlike most of the other quests, you won't actually have to fight any bosses for Sir Ansbach, but his quest is intertwined with that of Redmane Freyja and Lady Leda to some extent.