When a creature you can see within 5 feet of yourself makes an attack against you, you can take a Reaction to make one attack with a Melee weapon against the attacker. You can draw a weapon as a part of this Reaction. Resolve your attack before the triggering attack. On a hit, the triggering attack automatically misses you.
Once you use this feature, you can't use it again until you finish a Short or Long Rest unless you expend two Battle Dice (no action required) to restore your use of it.