In Japanese folklore Mekurabe is a strange yokai created when many skulls group together to take the form of one gigantic skull. It appears at night and silently challenges people to staring contests. Reports indicate that this strange phenomenon begins with a large number of skulls rolling around before they form into the giant skull, which then begins staring at you. If it loses the contest it will crumble and disappear, but if it wins...actually no-one knows what happens if it wins.
Tsukioka Yoshitoshi

'Hundreds of Human Heads Appear to Kiyomori at Kukuhara' - Tsukioka Yoshitoshi, 1890.

'Taira Kiyomori Haunted by Strange Sights' - Utagawa Hiroshige, 1845.

Toriyama Sekien

Tsukioka Yoshitoshi