I don't know who any of the PC's are, but that sword is Foeturner, a malignantly evil blade of epic might.
The plinth it hovers over was miraculously undamaged (possibly by intervention from Foeturner itself) following the magical siege of the fortress of K'feyne, (an elven archmage) whose collection of magical objects was quite renowned. Of course, that siege was years ago, and K'feyne has since moved on to another location... but apparently he forgot Foeturner.
Foeturner
Vicious Bastard Sword +3 (Intelligent, Telepathic communicator)
Alignment: Chaotic neutral
INT 17, WIS 10, CHA 17
Skills: Bluff +13, Diplomacy +13, locate object 3/day, clarivoyance 3/day
(58,000 gp)
Foeturner exists to destroy parties. He carefully allows himself only to be chosen by weak-willed individuals of simpler mindset than himeslf. (in the illustration, you can see Jameri the Unflinching poking Foeturner with a stick, partially at Foeturner's own suggestion) He regularly uses his own claravoyance to spy on other party members, just waiting for them to slight his wielder in any way, no matter how minor. He then communicates with his welder, using his high social skills to turn the most minor incedents into full-blown arguments, alternately goading his wielder into pressing the issue, and assuring him that he is completely in the right.
Foeturner never acknowledges his ego to anyone but his chosen wielder. If he finds his wielder unworthy, or if he is pressed into the use of a wielder other than his chosen one, he may use his locate object ability to subtly lead the unworthy wielder to another weapon they may prefer, and empathicly hint that his chosen one gets him.