Mystics increase in power by absorbing enemies. Each Mystic has a Mystic Sword, Mystic Gloves, and Mystic Boots. If a Mystic finishes off an enemy with one of these, they will absorb it. As long an an enemy is absorbed, it will give the Mystic a statistic boost depending on the power of the particular enemy absorbed. As well, depending on which Mystic item was used to absorb the enemy, the Mystic will gain an ability.
Monsters increase their statistics and abilities by absorbing enemies into their own body.
At the end of combat, a list of defeated monster-type enemies will appear. You may choose one for the monster to absorb, and it will gain a random ability from it. If a monster has enough of another type of monster's abilities, it will become a monster of that type and take up its statistics. Monster abilities tend to be weak, since they are geared to be used against your party, and thus rarely deal more than 999 damage. Mechs also gain abilities from enemies.