The person casting cursna is a GEO. It allows for her to stay in longer with an Indi spell instead of running out and losing the mob debuff. Since the doom takes so long to get off, you have lots of time to stay in until you "absolutely have to" run out.
This one isn't impressive due to the exploitable weakness by stacking enfeebles, but hey must of been fun to go rng how was your dmg from 100%-75% on Shark I would love to see numbers.