You gain the following benefits.
When you use the Warder's Intuition benefit of your Mark of Warding feat, you can roll 1d6 instead of 1d4.
When a creature makes an attack roll against you or a creature you can see within 30 feet of yourself, you can take a Reaction to impose Disadvantage on that roll. You can use this benefit a number of times equal to your Proficiency Bonus, and you regain all expended uses when you finish a Long Rest.