At-will, std, ranged, 1 mana; you take command of an active spell.

Roll your spellcasting skill vs the spell's DC. On failure, nothing happens. On success, you can redefine the parameters of the spell to your liking, such as:

• The spell's targeting
• Who the spell considers "enemies" if it is able to distinguish
• For summoning spells, you take command of the summoned creature

This works on any ongoing spell with a duration. However, if you ready an action to do so, you can use this to commandeer a spell as it is cast, which allows you to affect spells with no duration as well.