[Celacena]

the chromoatic demon isn't that difficult, but there is a problem with getting the xp for it! If you read the notes and pay attention to the imp etc, you'll realise that the way to take out the 4 sets of monsters partly involves the fan and poison gas.

if you get the CD to follow you into the slime room and shut the west door, if the fan is on or not, the room fills up with gas. the CD is susceptible to the gas and it will eventually kill it. if the gas kills the demon, the xp is not awarded, so to kill it, I suggest that you weaken it in the slime/gas-chamber and then deliver the killing blow yourself.

a backstab may do it although I usually use something with guaranteed damage, as otherwise you might leave it a couple of HP which the chamber inflicts.

the forms of the CD are immune to different attacks, but that isn't a problem as it changes form so often that it is not usual for it to get stuck as an immune form in the slime chamber.

the easist way I have done it is for a thief with HLA to spike trap the area it appears in - normal thief traps may do some harm to start off the damage. lower resistance is something I ususally inflict on that kind of boss too.

good luck