Oh, I can do that too.
The ritual to ruin an anime convention is as follows: take a large hefty bag full of manure and drag it into the center of main programming during cosplay or (failing good timing on your part) the vendor room of the anime con. After grounding and centering, cast your circle in whatever way your tradition dictates. Then proceed to throw the manure at any people nearby while screaming the following incantation: “ATTACK ON TITAN IS AWFUL. SAILOR MOON IS OVERRATED. STUDIO GHIBLI IS SHIT. THE CARDCAPTORS DUB WAS THE BEST VERSION OF CARDCAPTOR SAKURA.” Repeat for two to three hours, and you will have successfully performed the “ruin an anime convention” spell.
The threefold is unfortunate though, as it usually involves jail time or heavy fines.
New UnCONventional: Charm Offense