The Prism Psynergy series is one of the strongest groups of Mercury Psynergy available. It receives heavy usage in both games, as each level of the technique is very powerful for when it learned and retains much of that power for a long while afterwards, even outdoing the Jupiter-based Plasma Psynergy series it is paired with in the Hermit and White Mage class series, at the cost of narrower range. Being available to those two class sets and the Pilgrim (Mercury) series, it is available to all Adepts except Isaac and Felix.
Prism: "Attack with ice crystals." It appears as a single, massive piece of ice slamming into the target party and shattering. Prism is learned at Level 6, hits three targets with Mercury power of 40, and costs 7 PP to perform.
Hail Prism: "Attack with ice crystals." It takes on the form of four individual Prism attacks striking in succession. Hail Prism is learned at Level 20 by the Pilgrim (Mercury) and 22 by the Hermit and White Mage, hits five targets with Mercury power of 90, and costs 16 PP to perform.
Freeze Prism: "Attack with ice crystals." It appears as a spectacular barrage of about 12 Prism icebergs as the camera swivels around the battlefield. Freeze Prism is learned at Level 52. It hits five targets for Mercury power of 190, and costs an immense 32 PP to perform.