Acheronian clearsteel (from the PSCS Chapter 7) is basically glass as hard as steel that can be forged into weapons. In my Planescape campaign, I've got a bladeling psychic warrior wielding a large, Monkey Gripped greatsword. I set the players against an illithid servant of Ilsensine (infiltrating a temple of Maanzecorian after that god bit the dust *coughcough*don't know why*cough cough*) and its advanced umber hulk slave. Anyway, the player came up with the very good idea of screening his gaze through the clearsteel weapon in order to avoid the umber hulk's confusion gaze attack. I was quite impressed, as he had only gotten the sword made of clearsteel in order to demonstrate his plane of origin.
I adjucated that, each round that he held the sword in front of him and didn't attack with it, he didn't need to make a save against the gaze. So instead he spat his Exhalation of the Black Dragon at the thing, burning out its eyes and fixing the problem for everyone. Damn umber hulk low touch ACs! But huzzah for umber hulk tremorsense. They were disappointed when it still clawed away at them even after its eyes had been reduced to smoldering, fuming craters.
So, I just thought I'd inform the community that Acheronian clearsteel does more than just look cool (even when used for a weapon like a Large greatsword that can't take advantage of the improved concealability). And comment that the fight was excellently cool.
Any DM who wants to speed up combat should consider implementing the Massive Damage Threshold rule as in d20 Modern.
Very cool idea and excellent ruling, Rhys! Oh, and kudos for having such creative players!