Your experience in combating spellcasters grants you the following benefits.
Abjuration-Breaker
Whenever you make a ranged attack roll, you temporarily disrupt protective magic affecting the target. For the duration of the attack, the effects of spells targeting the creature, such as Mage Armor, as well as the properties and powers of magic items worn or carried by the creature, are suppressed and don't function. The target of the attack can't take a Reaction to cast spells such as Shield in response to the attack or damage.
Antimagic Shot
When you score a Critical Hit and the target is affected by your ValdaGunslinger feature, it also impedes the target's ability to cast spells. While the projectile is lodged in the target, it can't cast spells or take the Magic action. Additionally, the target has Disadvantage on Constitution saving throws it makes to maintain Concentration.
Inured to Magic
When you fail a saving throw against a spell or magical effect, you can take a Reaction to roll 1d6 and add it to the roll, potentially turning the failure into a success.