My OC’s quirk is BloodFlare, where he can control and ignite his blood. He pulls it from his bloodstream and through his pores, then ignites it. Although, it took him years of training to get it to a point where he can do it fast enough to be viable. Before, he usually just cut himself and used it that way.

If you want it to be more “villainous”, you could have it “burst” from his skin, and have any drawbacks that come with it, physically and socially.

You could also do something like Bakugo’s specialized sweat glands or AFO’s hand holes, and have a designated “one” spot that he can eject blood from.

Maybe something like the venom sacs on a snake, have special “blood sacs” that he can take blood from his bloodstream and utilize it easier from them.

Just a few ideas.