Deathbird (Liurnia of the Lakes) is an optional Field boss introduced in Elden Ring. You don't need to defeat this boss to progress further into the game. The birds are graveyard fire keepers ...

“Hatchet used in ancient sacrificial rite. A Deathbird is depicted as a malevolent deity. The Sacrificial Axe can be obtained by defeating the Deathbird (Weeping Peninsula) north of Castle Morn ...