I couldn't sleep, so decided to check out Shrimpo. Fire and lightning resistance are 50, poison and spiritual are 100, with 1416 hit points (and he can cast restoration to heal). He is level 30, does melee damage of 16-56 with a 95% chance to hit, and has an armour class of 127.
He is fast and agile, so hit and run tactics do not work as well as they do against some other creatures. Burning Wall does work (slowly), but getting on the other side of a group of trees and casting Meteorstrike as quickly as possible does do a bit more damage. Burning Wall would have worked better for me if I had more practice getting closed loops; Shrimpo is good at finding a way out if there is one, and doesn't usually try getting through the wall if there is another path that isn't too much longer.
Level 5 of Hell Spikes finishes him off fairly quickly (level 3 or 4 should work almost as well). He is smart, though, and will avoid the spikes as much as possible. The best approach is to stand on the other side of a group of trees / gravestones and cast it right in front of him as he approaches (he has to slow down to get through and is not as maneuverable).
I didn't try Blind on him, but that should help quit a bit. While blind, he could not attack you, so should be an easy target, and he might not be able to find the safest way off the spikes.
If you use a shadow potion, or cast Fade From Sight, I think you can cast area effect spells that do not need a target (such as Hell Spikes) near an opponent and not become visible (they can not counterattack). Warriors can use this with their spin attack to easily defeat any opponent (though that would be boring).
