Helm of the Sentinel
Wondrous Item, Rare (Requires Attunement by a Creature with the Mark of Sentinel)
Cost: 4,000 gp
This helm has 3 charges. While wearing it, you can use any of its properties. It regains all expended charges daily at dawn.
Counterspell
You can take a Magic action to expend 1 charge and establish a defensive ward with a contingent Counterspell. The next time you can see an unfriendly creature within 60 feet of you casting any spell that either targets you or causes you to make a saving throw, the Counterspell immediately takes effect whether or not you want it to, as if you had cast it using your Reaction. Wisdom is your spellcasting ability for this spell. The ward ends immediately after Counterspell takes effect or at the next dawn.
Protection
You can take a Magic action to expend 1 charge and cast Protection from Energy on yourself.
Deflection Field
You can take a Bonus Action to expend 1 charge and cast Shield of Faith on yourself.