An upside-down † symbol, also called St. Peter's Cross.

Nowadays often used as a satanic or anti-Christian symbol. It originally represented the Christian legend of how St. Peter was crucified upside-down because he felt unworthy to be crucified in the same manner as Jesus Christ.

Related characters: 
[[Shiroko (blue archive)]]
[[Suigintou]]
[[Satanichia Kurumizawa McDowell]]
[[Horikawa Raiko]]
[[Koakuma]]
逆十字