The Gashadokuro (がしゃどくろ, gashadokuro) or Odokuro is a large skeleton youkai born from a massive gathering of skeletons of those who died in war and those who didn't receive a proper burial.
Gashadokuro wanders the night producing a "(ガチガチ), gashi-gashi" sound and will crush and devour any living thing it sees, human or not. According to Japanese Folklore the only way a Gashadokuro can be detected before it appears is by "hearing a ringing in one's ears".
In Ten Desires during Sanae's Extra Stage, Sanae's idea on the youkai trump card was a Gashadokuro (shortly disproven however). It is unknown whether there are any Gashadokuro in Gensokyo or not.