How do i kill Effritus? I'm on a quest called mastering the arcane, and I'm positive I need to kill this bat dude to get one of the objects I need. But I can't figure out how to kill it... HELP!

http://worldofpacifism.com/?p=175 incase you need to see a photo, this is what he looks like.
I'm on a mac...

Just as you get within striking distance, hold down the "ALT" key
and then hit the "F4" key.

(Then, go outside and meet people in RL.)

You do not need to kill him, the entirety of this quest happens inside Shadowfang Keep, a level 20-26 dungeon. You need to kill baron silverlaine (a boss), loot his body to get his enchanted crystal. While you are in the instance you should see the moontouched wood and the ghostly essence you need to collect. If you have any other questions wowhead.com is your best choice. Just search the quest you are on and there is a comment section underneath that people talk about details of completing the quest.
P.S.> guy above me; alt f4 doesnt work on macs guy