Sword of Selvetarm

The Sword of Selvetarm was an intelligent holy sword of Selvetarm's church.

Properties
The sword's properties changed depending on who wielded it. Its true potential was only usable by evil drow.

Evil people in general
In the hands of an evil person, who wasn't a drow, it worked as a simple +2 longsword. The sword's intelligence tried to dominate the non-drow wielder into working for Lolth and Selvetarm.

Non-evil people
In the hands of any person who wasn't evil, the sword was outright dangerous. It stunted the wielder's vitality, killing those too weak, which was impossible to restore as long as the owner clinged to the sword.

Evil drow
In the hands of an evil drow, the sword showed its true potential. It worked as a +5 elf bane unholy vorpal longsword with a large amount of additional powers bestowed on the user, both physical and magical.

On the physical side, the sword heightened the wielder's agility and abilities to hide. Furthermore, the wielder could rage like a barbarian.

On the magical side, the sword allowed the casting of spider climb and web as often as the user wanted and of fire spider once every day. Once per month, the user could summon a yochlol, who opened a channel to commune with Lolth or Selvetarm.

The sword's intelligence
The Sword of Selvetarm was an intelligent weapon. It couldn't actually talk, barring telepathy, but it could shout Selvetarm's name during any battle. Shouting Selvetarm's name was a common practice among his followers, for they believed killing someone while shouting the name would hand over the killed one's soul to the Spider that Waits.

It generally hated to be not used in a battle and actively urged its owner to enter the fray.

Creation
The sword was created by Selvetarm, the drow demigod of warriors. The Sword of Selvetarm was created as a tool to promote Lolth's agenda, a deity to whom Selvetarm was practically enslaved to.

It was a longsword instead of a heavy mace like his actual favored weapon, because it was made to strengthen that branch of drow warriors, that trained in the usage of two-handed weapons.

By 1372 DR, the sword was lost for decades but its recovery was believed to be a matter of time.

Destruction
The sword was difficult to destroy. The only way to destroy it was to bring it into the Demonweb Pits and hurt either Lolth or Selvetarm with it.