[Aerich]

You're talking about the fire salamanders and tarnished sentries, right?

Here's some tips:

1) Buff up your best melee characters to the max including with Protection from Fire
2) Use Protection from Normal Missiles or Entropy Shield
3) Use blunt weapons
4) Cast tough summons like earth and fire elementals
5) Cast Haste

I use 2-3 characters to hammer down the sentries, and the rest take down the salamanders from range. Be careful how far you move, as you may trigger more and more of these. Don't bother trying to sneak around - Tarnished Sentries can see you, even if you have Non-Detection cast on you. Just seek and destroy.

If you have to, run out and go back to the Aquarium to rest and recover, then charge back in.