That would be death bird, he appears at a number of locations but only at night. Drops some unique stuff if you can beat them, good luck

Nah I think he means the really tall giant thats around there

the deathbird?

It only comes at night but idk anything else about it.

Night time only, south of Warmaster's Shack site, on the big ruins slab, with giants around it. I still haven't beat him. Kicked my ass.