Psion's Blade

The Psion's blade, also known as the Psion's Blade +5, is an enchanted Two Handed Sword +5 that can be found in Baldur's Gate II: Throne of Bhaal.

In-game Description
''Some believe this massive blade to be of Drow origin, though others dispute this claim. However, all agree that this great sword was fashioned with a single purpose... to rid the world of the Illithid. Those who wield the Psion's Blade are immune to the Mind Flayer's psionic attacks. The bewildering gaze of Umber Hulks, often found serving the Illithid, are similarly rendered harmless.''

Acquisition
The Psion's Blade is hidden in one of the lava-surrounded strongboxes in the Outer Chambers of Yaga-Shura's Lair, hidden in the Marching Mountains. It can be found in the second tier room on the right-hand side of the map. It is guarded by Flameskulls, Fell Cats, Burning Men and Salamanders.