Two nightmares I have encountered so far...

[macBos]

I recommend same tactic as Batty

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Invisibility spell works great for me - at first killed all small ratlings except boss, then it was much easier

[Sorez]

If you don't mind losing XP, you can kill it in one hit.

http://steamcommunity.com/sharedfiles/f ... =327947596

(Spoilers of the boss name in the link.)

[Sir Tawmis]

I actually have a funny Leprechaun story... He has good reason to hate my party!
When we were exploring some underground tunnels, back in Twigroot I think, killing numerous ratlings in the damp darkness, we eventually came across a blurred silhouette, which I thought was just another ratling vagabond ready to slit our throats. I cast the poison bolt spell, and only when it hit the creature did I realize that it was actually a Leprechaun I'd shot at! D: (First encounter) He high-tailed it immediately down the hallways, losing damage over time from the poison, culminating in him vanishing into the darkness right after having locked a metal gate between him and my group! I considered reloading, but decided it would be more immersive to continue playing, so I did.
Now he's unleashing his sweet revenge on me whenever he gets the chance! xD I keep screaming, "I'm sorry!I thought you were a pirat!" over his mad cackling and reckless bomb throwing, but I don't think he wants to hear anything I have to say. D:

Oh my Gawd, that's freaking hilarious! I can totally see you shouting, "Damn it! I said I was sorry! I said I was - seriously? You're going to throw fire bombs? I said I was sorry didn't I? Let's talk this over! Son of A! You just killed my wizard! You bastard! Now it's personal!"

For the Ratling room,

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I cast invisibility and went in the room to do recon. When I returned to the entrance, the stupid rats followed me one at a time so I effortlessly killed them all. The big rat stayed in the main area and was then easy to finish off without his support team.

I recommend same tactic as Batty

SpoilerShow

Invisibility spell works great for me - at first killed all small ratlings except boss, then it was much easier

Ah! Very cool. I haven't got that spell yet...

If you don't mind losing XP, you can kill it in one hit.
http://steamcommunity.com/sharedfiles/f ... =327947596
(Spoilers of the boss name in the link.)

How the heck did someone even figure out to do that? Some... creative thinking...

[BouH]

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I actually use invis frequently, in this case after door closed use it, go to little pocket near the enter. And bear with rage potion and supply of energy potions made the rest (with double weapons bear can attack twice per move). Big boss wwas killed in main room by vellknown round way

Real nightmares is mimics