Skeleton Fortress

Possibly a new biome in the nether, structure in the overworld, or a dreary, dead, entirely new dimension. An area with walls surrounding a graveyard or skeleton village with an event similar to pilllager raids except instead you go to them instead of them coming to you, skeletons will be guarding the inside of these walls with bows, axes, and swords, after a certain amount of waves or skeletons are defeated a new boss skeleton will spawn much larger than other skeletons, stronger, and much higher health pool, one of its drops could potentially be an enchanted bone to give to a tame wolf to convert it too a skeleton dog.