This is a room that will cost you a Dispel sepll and a Cure spell and nothing more. You enter at the North and the corridor narrows to a single entrance with a Lightning field blocking it. Past the field is a vast pocket of Poison fields that lead to a good number of treasure chests (and two Mimics, one on either side). The only attack Mimics seem to perform, though, are spitting poison. Since you are already nearly guaranteed to be poisoned by the fields already, you can stand toe-to-toe with the Mimics and not worry. Send your hero with the least experience into this fight and let him reap the rewards with little to no risk.