This large sword is of masterwork quality and etched with runes. Some cultures would call this type of sword a fullblade.
The Foolblade was crafted by a wizard blackmailed into forging the weapon. The first recorded use of the Foolblade was against the crafter herself, whereupon her "added" abilities saved her life and ended that of her assailant.
To this day, the blade is sought out for its combat prowess. Unfortunately, the curse that goes with it is rarely spoken of, as it magifies a known weakness of fighting sorts. And due to its appearence, it is only rarely that both spellings and meanings of its name are taken into account (Full Blade vs. Foolblade).
While wondrously powerful in combat, it has a detrimental effect upon its wielder’s mental ability. To the point where the wielder is easily manipulated to the point of becoming a fool.
Generally speaking, Foolblade is enchanted to be incredibly sharp, and its wounds cut deep, leaving permanent damage. It leaps into its wielder’s hands, almost unbidden, whenever combat rears. In addition, Foolblade can temporarily increase the strength and fortitude of its wielder.
The drawback to the sword is that its wielder is rendered a fool, due to an amazing drop in intellect, common sense, and personal magnetism. Coupled with this drop in mental faculties comes a desire to use the Foolblade regardless of the tactical situation or sheer folly of doing so. Lastly, the only known means of being rid of Foolblade is through permanent death or powerful magic.
Not surprisingly, its generally freed up by death.
In D&D terms:
The wielder has the Quickdraw feat in regards to using the Foolblade.
The weapon itself is forged of adamantine and is +3, with the wounding and keen abilities.
The Foolblade wielder can cast Bull’s Strength and Bear’s Endurance on himself 1/day each, as if cast by a 15th level caster.
The wielder suffers a -6 penalty to Intelligence, Wisdom, and Charisma scores while carrying this blade.
Upon claiming the Foolblade, the wielder ALWAYS tries to use it in battle, even when sound tactics or common sense would dictate otherwise. It just appears in his hands.
Once the Foolblade is claimed by someone, the only method of getting rid of it is through permanent death (no coming back), wish, or a miracle spell.