How to make a weapon damage only one kind of enemy?

So what I want to do is make a sort of vampire slaying weapon, that is fairly OP, but only against vampires. Is there a way I can do this?

If you only want it to affect normal attack, just have the weapon use a certain element, let's say anti-vampire, then make the attack skill use weapon element (which is the default setting), then make the vampire have negative resistance to it.


Or you can edit the normal attack skill, add a check for the weapon, if it's the anti-vampire weapon and the enemy is a vampire, make it deal more damage

If you go the anti-vampire element route, make sure you give your non-vamp enemies an element rate of 0 for anti-vamp element. Otherwise, it will still do standard damage.