Servant of the Shard

Servant of the Shard is the first book of The Sellswords trilogy by R.A. Salvatore. It was originally book three in the Paths of Darkness series, but as it did not focus on its central character, Drizzt Do'Urden, Salvatore decided to make a a separate trilogy based on the events in Servant of the Shard, which ended in Road of the Patriarch.

"The Assassin. Surrounded by dark elves, Artemis Entreri tightens his grip on the streets of Calimport. While he urges caution, his black-skinned sponsor grows ever more ambitious. The assassin will soon find himself on a path his most hated enemy has walked before him—a path that leads to a place where someone like Entreri would never be welcome.

The drow Jarlaxle has ascended from dark Menzoberranzan with only evil intentions. The malevolent Crystal Shard’s influence on him intensifies until even the drow agents he brought with him grow fearful. When Bregan D'aerthe itself begins to turn on him, Jarlaxle will be forced to find a savior in the man he’s come to enslave."

Summary
Artemis Entreri and the rest of the Basadoni Guild continue their "war" against all neighboring Guilds of Calimport, killing many people. This time, however, there is a difference, which is that the Basadonis have a legion of drow (Bregan D'aerthe) on their side. Artemis Entreri sees the oppotunity to gain a sword, Charon's Claw, and goes for it. Meanwhile, despite his great willpower, Jarlaxle is being seduced by the power of Crenshinibon, or the Crystal Shard. Artemis Entreri feels that it is necessary to help him get rid of the artifact. The two come across a great opportunity to destroy the Crenshininbon in the form of the man named Cadderly Bonaduce, a Chosen of Deneir. They must take the artifact to the cave of a great wyrm, Hephaestus, in order for to be destroyed. Danica also comes along for the destruction of the Shard. Rai-guy, however, a cleric, traitor to Jarlaxle Baenre, tries to stop them. When the Crenshinibon is encased in a globe of darkness, the wyrm, threatened, breathes upon it and that being the way to destroy it, makes the Shard explode, which kills the main antagonist Rai-guy in a flash of blinding light that turns him into a crisp. The story is continued in Promise of the Witch-King, even though the Crystal Shard has been destroyed.