Devil Jaw's origins are not wholly known, other than it was crafted by heretical smiths from Baatorian green steel and the jaw bone of a massive Baatezu. Whether it was crafted there, or found it's way with a hapless traveller, Devil Jaw ended up the realms of dread and ultimately in the hands of Gregor in Barovia.
The spirit of the Pit fiend which the blade was crafted is infused within, and it hungers for Tanar'ri flesh. Granting the weilder full access to its power as a reward for slaying a fiend. For a time, this weapon was purified and became the Devil Foe, but with the Pit fiend's spirit returned, it has regained its former glory.
Devil Jawis a +3 Defending Unholy Greatsword of Bane vs Chaotic Outsiders.
Additionally, if you have killed a Tanar'ri demon within the last week, the weilder can release an empowered profane fireball (DC 20 Ref, 10d6 x1.5) as the spell fireball cast by a 9th level wizard, though half of the damage is considered profane and non-elemental.
Defending. A defending weapon allows the wielder to transfer some or all of the sword’s enhancement bonus to his AC as a bonus that stacks with all others. As a free action, the wielder chooses how to allocate the weapon’s enhancement bonus at the start of his turn before using the weapon, and the effect to AC lasts until his next turn.
Bane.A bane weapon excels at attacking one type or subtype of creature. Against its designated foe, its effective enhancement bonus is +2 better than its normal enhancement bonus. It deals an extra 2d6 points of damage against the foe. Bows, crossbows, and slings so crafted bestow the bane quality upon their ammunition.
Unholy.Upon command, an unholy weapon is imbued with unholy power. This power makes the weapon evil-aligned and thus bypasses the corresponding damage reduction. It deals an extra 2d6 points of damage against all of good alignment. It bestows one negative level on any good creature attempting to wield it. The negative level remains as long as the weapon is in hand and disappears when the weapon is no longer wielded. This negative level never results in actual level loss, but it cannot be overcome in any way (including restoration spells) while the weapon is wielded. Bows, crossbows, and slings so crafted bestow the unholy power upon their ammunition