Cursed seals

From Dscomics

Cursed seals are cursed black-magical markings to seal power given by evil beings. They can either transform someone or make someone's brain turn into edible gum whenever the applicant of the seal wills it, or can be used to compact with (a) demon(s) on one of someone's hands to execute "Demon Wave" techniques.

Other seals seal demons in people's bodies, giving them a tremendous amount of power from the demon.

Orochi, is the one who made several seals, as his demon can perform cursed seals without consequences. One cursed seal he made was used on D-Shadow to bound him to Orochi and give him a demon-like form.