Not a review - may do that later, but if you ever hear about a card being referred to as "Rhydon", as in, the Pokemon Rhydon, it is this card. The name comes from a joke made in the Mythos Busters Discord and it stuck, so that's the nickname I'm pushing for it now. I mean, the name of this card is frankly very long and hard to say, so of course, it needs a nickname and Rhydon is as good as any. It sounds vaguely like Shining Trapezohedron, if you pronounced it wrong, which let's be real, you probably did at least once.
When you would pay the cost of a Spell card, exhaust Shining Trapezohedron: Instead, test (X), where X is the card's resource cost. If you succeed, its resource cost is considered paid. If you fail, cancel the playing of that card without paying any of its costs (including its action cost). For the remainder of the round, you cannot play copies of that card.
This in theory looks like good Mystic card. As a Mystic you already want to stack willpower boosts. This lets you willpower not only to cast spells, but also pay for them. If you get to 6-7 willpower, you are almost guaranteed to be able to play 2-3 resources spell each turn for free. I'd say this pairs well with Jewel of Aureolus, allowing you to reveal more tokens and generate more resources and cards, but they both cost XP, and use same slot. But I can see funny Agnes 2x Relic Hunter build, where you want to use this,Jewel of Aureolus and Heirloom of Hyperborea and play as many spells as possible, while drawing insane number of cards while doing this. This would be deck with pretty large ramp up, but after getting set up, you should cycle through your deck at insane speed.