From publisher blurb:
Sing the song of darkness, and master the shadows!
With the Elven Shadowmage, a new 10 level elven variant class for Adventurer Conqueror King and Labyrinth Lord, you can play these arcane shadoweavers in just about any OSR game. Elven shadowmages specialize in using the darkness to do their bidding, and can perform many of the tasks that a human thief would, only using their unique magic to do so. They also learn a small number of 'normal' magical spells along the way, and are often confused with elven nightblades as they function as scouts and infiltrators.