My proposal for what we should do. I'd very much like feedback on what everyone thinks; don't want to feel like I'm "solo"ing this, but do think we should put down our actions before too long, and so far only Aslain has done so. (And me and Beldarion partially.)
Sulibor sends his Ogre with Aslain's lit torch along the right side of the room, and then follows the main party in the back. He will command the Ogre that when it sees a Beholder coming for it, it should take shelter behind the pillars, and then move back, trying to lure the Beholder into following him. If he hasn't been seen by the beholder or isn't being followed by the beholder, but hears an explosion, it should move to the center of the room and then back to the right, in a stronger attempt to draw the Beholder's attention.
Sulibor also recasts the expiring Magic Shields (Beldarion now, me next turn, himself the turn after). A Magic Shield on Aslain now to help him if Cicatrix notices him would also be good, and on Kip and Triock if he has the spell slots to spare?
If we engage the Beholder in combat, and it floats too high, Sulibor should cast Levitate on Beldarion and Triock so they can actually engage it in melee. (Possibly also on me, since my axe is a lot better than my bow? Lowest priority, though, so only with plenty of spell slots!)
Aslain keeps his fire swords sheathed as long as we haven't been noticed by the Beholder (not necessary if they don't give light) and takes point along the left side of the room, scouting for traps. Primary objective should be to gain the mirror back from Cicatrix, through theft or violence.
Beldarion and Triock keep their fire swords sheathed as long as we haven't been noticed by the Beholder, and follow a distance behind Aslain, taking care to move quietly and standing still so as to not give Aslain away if/when he makes an attempt at Cicatrix. I have very little idea about Triock's magical abilities, so if there's anything to assist there, that'd be very good to know!
Og'rialt and Kip follow after. If Cicatrix comes within range, and if it's clear that Aslain for any reason won't succeed in attempting to steal the mirror, then everyone with ranged attacks will shoot at her as soon as Aslain is away from the immediate vicinity of Cicatrix (Aslain with bow, Og'rialt with bow, Kip with sling, Dunward with darts). The explosion from Kip's sling is certain to draw the Beholder's attention, but I hope we can override that with the Ogre, and otherwise we'll just have to be certain to grab that mirror as swiftly as possible.
Once we see Cicatrix, we'll also see her dire wolf, which Beldarion and Triock could engage.
If we obtain the mirror, I don't know if it's bound to me, or if anyone can defeat the Beholder with it. I'll attempt to get clarification there.
If we don't notice Cicatrix, but notice the Beholder going to investigate the torch from the Ogre, we'll have to make a choice between attempting to ambush it, and attempting to continue sneaking past. Really want to hear people's opinions on that!
If Cicatrix has drawn the beholder's attention before we reach her, I'm also uncertain what to do, but we can probably strategize that next turn, still. We should probably wait for it to kill her, distract it while staying in the cover of the pillars, and grab the mirror?
RedFireGaming: I know I'm not Triock, but I do have daylight in my current spell lineup. Just tell me where I need to be before I cast it, and it should illuminate the whole room.
That'll be very useful once we engage the Beholder in combat, as it'll allow Kip, Beldarion and Sulibor to see clearly! I think your character has plenty of reason to cast it once you've moved up the stairs and see this dark hall here. As I suspect we sadly both lack telepathic communication, I don't think I can direct you as to where/when would be most useful exactly. *g*