[quote=@Raijinslayer]
<Snipped quote by Hebigami Shiho>

Revan: "I'm going to fucking de-de-de*sudden;ly breaks into a fit of sneezing* Dammit Ivory, can't you be something else, fuck!"

Also, Revan's only Half Demon, and his demon half has been rather diminished which means they'd probably think he's a low level demon at best. Them having a devil slayer will be a problem, as Revan will still take extra damage from that. Should Revan and Xavier be just as affected by Devil Slayer Magic as full demons, or just have it be 1.5x the damage instead of the full 2x.
[/quote]

I don't think Devil Slayer magic does extra damage so much as it one-shots them. In the canon Gray only had to hit demons once to beat them, regardless of how strong they were.

And Dragon Slayer magic also has insane boosts. Literally all magic doesn't even effect Dragons except for Dragon Slayer magic. Even Curses don't effect them. Going from zero to anything is pretty good considering Dragons are alleged to be the strongest things to ever exist.