Another Crazed Mage is a side quest in Divinity: Original Sin. After defeating the Source Abomination mini boss, you can walk upstairs the ramp to reach a room with this crazed mage.
Once you enter the room, the mage will tell you that you need to find a way to disarm the trap in the room, otherwise your character will die.
The character which triggered the quest must not move, otherwise an explosion will kill him and potentially your whole group. This might be a good time to quick save with F5!
To solve this puzzle, unlock another character from the party by clicking and dragging their portrait to the middle of the screen. This will ensure other characters do not move.
After this, use your other character(s) to find the hidden switch and disable the trap.
The location of the trap switch is shown highlighted on the screenshot above.
