The Unwelcome Warlock - Lawrence Watt-Evans

Hanner the Warlock knew his days were numbered. The Calling pulled at him ceaselessly now, and his ability to resist had begun to crumble. So he determined to find a place where the Calling couldn't reach him...another world, located through a magic tapestry. Every warlock knew that the farther he was from Aldagmor, the weaker the Calling was - and the weaker his magic was, as well, but that was only a secondary consideration. That weakening had given Hanner the idea to find, or make, a place so distant from Aldagmor than the Call couldn't reach it at all.

Unfortunately, the Call took him anyway. And that's where his story really gets interesting. Because the Calling wasn't what everyone believed. And, when the wizards who had been Called over the decades suddenly wake up again at the object doing the calling...and find themselves without their powers...the world may never be the same again!