Category
By summoning a swarm of Wyldling spirits and Rat-spirits, you can invoke sheer pandemonium. They'll crawl the wails, manipulating mundane objects randomly, and causing sheer chaos. Any non-Ratkin in the room is hit with the Delirium.
System
Spend one Gnosis; everyone present rolls Willpower (difficulty 8). Anyone who fails this roll gets hit by the Delirium, just as if they were human. Humans are automatically affected, but move one step up the Delirium chart for each two successes they get.