Skeleton is a rare boss in the world Nunchago. His spawn rate is 5% in the battle areas in the world. His his stats are 80HP 8POW 2DEF so if you are just beginning and you don't have 7-9friends, we suggest you run. He drops rare items like the Golden Bone Axe and some pieces of the Skeleton Armor.
Skeletron, Skeleton armor, and golden bone axe by ShockwavedoesMC