[Espy]

probably can also only be defeated by torches or something.

A disillusioned dancer who you find sprawled in the snow in front of your party's keep one morning. Getting them indoors is a bit tricky, but becomes easier after the mage figures out that moving half-incorporeal bodies is significantly easier with the use of magic.

Halfway through the main storyline, your bard is revealed as a spy for the main antagonist, and their betrayal leaves a gaping hole in your party lineup. If you've completed the first part of Mer's companion quest, you can take them along with you on your travels, which allows you to eventually encounter the trigger for the second part of the quest, after which her bardic abilities are significantly boosted.