Well obviously anything that reduces damage from demi-human would help like thara frog card, poo poo hat, combat knife, etc. Also being a ranged attack a Noxious card and Long Mace would also reduce it. One more thing to consider is that Soul Destroyer has two separate damage portions. The physical half can be elemental, but the magical portion is a non-elemental attack. I've heard rumors that the magic half is blocked by GTB, but I personally never noticed whether it does or not. Then there is always pneuma of course.
It's a strong attack, but has a high skill delay so you should focus on killing the person before they get the chance to hit you 2-3 times. Unless of course you're on a server where a Kiel card would be easy to get.
