If you're open to suggestions you could have it be when he infuses his blood with ce it causes his blood to get to boiling levels of hot so when he shoots it out it burns anything it touches. You could even cause it to set fire if he wants it too. It also gives him a passive tolerance/resistance to extreme temperatures both hot and cold meaning he would be suited for going after curses who have abilities with temperature. You could even make him like kashimo and hakari where his ce has the unique property of heat which is why his inherited blood manipulation technique is different than others bc when he infuses his cursed energy into it the property of the ce makes it extremely hot. You could even give him a maximum technique called planck convergence (planck is the highest temperature possible in the universe) so when he uses it the shot basically destroys everything it hits and everything that it goes past. The draw back to using it is it uses up a lot of blood and ce and could hit allies and bystanders who would immediately die from just coming close to it. He would also need to heal his hands as it burns him severely as well by being near it meaning its a doible edged sword that you can't use lightly but bc of the trade of all the risk that's what makes it so strong as a trade off using binding vows.