No. 4 - Xarpus
I could’ve ranked Xarpus a spot or two higher, given the fact that it is the penultimate boss of the raid, but I chose to keep it just outside of the top three due to the fact that it doesn’t actually attack you. This fight is all about playing defense, and as they say in sport, defense wins championships.
At the start, simply stand on top of the zombie spawn to prevent Xarpus from healing as much as possible. When the fight itself actually begins, all you need to do is move away two spaces when he launches poison. You should not run out of tiles before this phase of the fight.
The final phase of the fight involves two things: attacking Xarpus, and not attacking Xarpus. Stand in one of the four corners (or thereabouts), and only attack the boss when he is facing toward one of the other three corners. Attacking him when he is facing you will result in massive poison damage.
This encounter is really one requiring a smart systemic approach and strategy, rather than brute force.