Rise of the Thrall Lord
This dark, glittering steel alloy holds an attraction to souls recently released from their bodies. If a thinaun melee weapon is touching a creature when it dies, that creature’s soul is sucked into the weapon rather than passing on to its final reward.
The soul remains in the thinaun weapon until the weapon is destroyed or another creature dies while touching (or wielding) the thinaun weapon (the new soul displaces the old one). Raise dead, resurrection, and similar spells won’t bring back a creature whose soul is thus trapped unless the caster has the weapon in his posession.
Because the soul is nearby, reincarnation, raise dead, resurrection, and true resurrection require half has much of the relevant material component to cast if the soul is within a thinaun weapon. Only melee weapons made primarily of metal can be crafted as thinaun weapons.
Thinaun adds 10,000 gp to the cost of light weapons, 15,000 gp to the cost of one-handed weapons or one head of a double weapon, and 20,000 gp to the cost of a two-handed weapon or both heads of a double weapon.
Source: Complete Warrior, page 136