Spell Engines

Coveted devices of the Seree, mentioned prominently in several adventures. The Seree usually chose a guardian for each engine, who would protect it for a period of servitude, absorbing magic and wisdom in the process. These guardians became dragons. The failed wizard-apprentices would go on to become vault servants as undead construct type of guys.

The greatest Seree magics relied on spell engines—vast devices built to collect, harness, and broadcast magical energies for sorcerers to use many miles away. Spell engines were always built in secret vaults to protect them from theft, war, or destruction.

—from 18 The Full-Dark Stone.