Ply Psynergy series

Ply, Ply Well and Pure Ply are a series of Mercury Recovery-class Psynergy featured in both versions of Golden Sun. It is available to the following classes:
 * Swordsman (Venus)
 * Swordsman (Mars)
 * Dragoon
 * Water Seer
 * Mariner

Psynergy Spells
Ply: "Restore 100 HP with faith's power.": This spell costs 5 Psynergy Points, restores 100 HP, and affects one target ally. It is available at Level 1 for Swordsman (Venus), Swordsman (Mars), Dragoon, and Water Seer, and at Level 2 for Mariner.

Ply Well: "Restore 200 HP with faith's power.": This spell costs 8 Psynergy points, restores 200 HP, and affects one target ally. It is available at Level 16 for Swordsman (Venus), Swordsman (Mars), Dragoon, and Water Seer, and at Level 17 for Mariner.

Pure Ply: "Restore 1,000 HP with faith's power." This spell costs 12 Psynergy Points, restores 1,000 HP, and affects one target ally. It is available at Level 34 for Swordsman (Venus), Swordsman (Mars), Dragoon, and Water Seer, and at Level 35 for Mariner.

Analysis

 * This spell is the single-most potent Recovery Psynergy in the game, short of reviving a fallen ally. As for whether it's the most practical, most would award that honor to Pure Wish.