Wyvern's Tail is an enchanted morning star +2 which has the ability to deal 5 points of poison if a save vs. poison upon every hit with this weapon isn't successful. It deals 2d4+2 points of crushing damage, has -2 THAC0 bonus, a speed factor of 5 and it weighs 9 lbs. This item appears in Baldur's Gate II: Shadows of Amn and Baldur's Gate II: Enhanced Edition.
The large spike at the head of this morningstar is actually the lethal stinger of a wyvern. The mage-fighter Sedej created this weapon, using his magical abilities to keep the stinger capable of producing poison. The magic he used has actually made the Wyvern's Tail a living weapon, that pulses with life in the hands of its wielder.