Tales of the Valiant Players Guide (pg. 268)
3rd ring Arcane, Abjuration
You attempt to interrupt a creature in the process of casting a spell. If the creature is casting a spell of 3rd circle or lower, its spell automatically fails and has no effect. If it is casting a spell of 4th circle or above, make an ability check using your spellcasting ability. The DC equals 10 + the spell’s circle. On a success, the creature’s spell fails and has no effect.