The Summoning

"From the depths of the Demiplane of Shadow comes a new magic so mysterious it confounds even the Chosen of Mystra.

From beneath the dune seas of Anauroch escapes one of Toril's most powerful and ancient evils -- the phaerimm.

From Evereska, the last elven refuge on comes word of invasion.

From nowhere appears a group of enigmatic sorcerers determined to destroy the phaerimm and save Evereska... for purposes known only to themselves.

From the author of Crucible: The Trial of Cyric the Mad, Beyond the High Road, and Death of the Dragon (with Ed Greenwood) comes the most Realms-shaking event since The Threat from the Sea."

Summary
The Siege is the first novel in the Return of the Archwizards novel trilogy. It focuses on the elf Galaeron Nihmedu, an Evereskan Tomb Guard, as he patrols the desert border south, coming across a band of tomb robbers his patrol intervenes and inadvertently releases a great evil imprisoned below the desert.