Couple of notes this episode. The Samhain Festival is actually called the Magic Festival in Japanese, but it’s written Samhain everywhere in English. It really has little to do with magic and more to do with the origins of Halloween, so I have no idea what Trigger is thinking.
As for the Grand Triskelion revealed last episode, we have more information now. In Japanese, the kanji given for it are 究極魔法, meaning ultimate magic. That should give us a bit more to work off of if they didn’t already say it in the Witchpedia.