It has an impressive Ward ability, requiring an opponent to sacrifice a legendary artifact or legendary creature to target it with spells or abilities
It's sort of like a stronger Tooth and Nail
To determine the total cost of a spell, start with the mana cost or alternative cost you're paying (such as a flashback cost), add any cost increases (such as kicker costs), then apply any cost reductions (such as that of this ability)
As we cast our commander more, the buff stacks up and it can begin comparing to Dictate of HeliodDictate of Heliod and then Collective BlessingCollective Blessing
In fact, using the ability might be better than casting Deveri as a 3-drop since it skirts counterspells
Rhystic Study (blue, 3 mana): Taxes opponents' spells into free cards