Armor for Haschel that can only be found in a chest in Rouge. Like the metal armor Armor of Yore before it, it blocks the Status Ailments that are more annoying than they are threatening. Petrify and Can't Combat will kill you. Bewitchment, maybe. Confusion, eh. The Poison, Stun, & Arm Blocking that Satori Vest protects against, won't. But they slow you down, take time to deal with. The DEF and MDEF is a much bigger deal, but the immunities are not negligible.
It has more Defense and less Magic Defense than Armor of Yore. It has only three more points of DEF and five more MDEF than Energy Girdle, which was possible, if hard, to get way back in Home of Gigantos
Satori Vest comes after the Saint Armor for Haschel that is totally balanced at 34 DEF and 34 MDEF. Saint Armor is less of an upgrade than a tactical option for battles with a lot of magic damage. And Satori Vest is less of an upgrade, but only an option for physical battles. After large early gains, the developers decided to not improve his armor very much. Haschel's becoming less like, bad to the bone, and more like, battered to the bone, if his armor has anything to do with it.