You set out on an errand from the Wizards' Council of the Isle of Anduin to get the ingredients for a dark ritual copied from Crelanu's Book. The ritual is designed to summon the greatest evil in the land, who they think is Asheviere. However, a much more sinister evil emerges....
You start as a Silver Mage, and can take advantage of your teleportation and cold resistance as you fight a variety of enemies, while being able to recruit different things in each scenario (although always mages).
This campaign is only available from the campaign server.
This thread in the forum: http://forums.wesnoth.org/viewtopic.php?t=2032