Soul gems

Soul gems are items that allow the player to capture monsters, captured monsters to act as guard/attacker, capture monsters can be used for development of Transformation Seals. Soul gems have 5 levels, each being able to capture different monsters, every higher level gem can capture lower level gem monster.

At level 3, monsters become increasingly difficult to catch, requiring many tries depending on how low their health is (the lesser health a monster has, the easier it is to capture). This can be fixed by using higher level gems, which make capturing monsters more likely.