Skull
Dropped by
farming it
Cavern Skeletons drop it and the roll is unkind. Statue spawns are penalized on top of that, so a statue farm is a much slower route to it than natural spawns are. Battle potions and water candles in a real cavern beat a spawner room here.
what to wear it with
Put it on with the Robe and the silhouette reads as a Dark Caster. That combination is most of the reason anyone hunts for this.
where it came from
The item exists because of The Legend of Maxx, a long running fan comic. In a 2012 strip the lead character strips a skull from something he had killed the issue before, wears it, and then discovers there is no getting it off again.