After reaching the second level of Irenicus' Dungeon, Gorion's Ward can find a cell from which a 'commoner' named Frennedan pleads for his freedom. His key can be found in a trapped chest outside the cell.
Frennedan is actually a doppelganger in disguise. If he is released, he immediately turns on the party when next they are in combat or after a few minutes have passed. Upon opening his cell, however, you also have the option to attack him. Regardless of how he becomes hostile, he always reverts to his natural form when he does.
If you refuse to free him, he shapeshifts into a child in an ill-conceived attempt to make his plight seem more desperate.
It is recommended to have every member of the party engage Frennedan with ranged weapons till He reaches the party, as He is able to regularly hit individuals with maximum Armor Class available at the time