Sisters of the Moon, Who triggered Astral Purge?

Hi guys,

New account here, I’m just looking to find out who was the one who initially triggered Astral Purge. For whatever reason, my guild’s logs are private, but if say the log was this one , how do you find out who triggered AStral Purge and when?

Thanks guys.

Friendlies cast Astral Vulnerability (ID: 236330)