Samantha's Anger

"loading time" refers to the Casting Time. Just stand within the magic circle (the Disciples will ignore you so long as you do not disturb them), target the and "use" this skill and, 5 seconds later, the goes boom!
The respawns quickly so you can just go back and forth between two circles. Just be VERY sure you keep a watch on the nearby to avoid him.
This skill is available when is active.