Retaliate
ArmDef
Reflect a portion of melee damage taken.
Rolls between 3% and 18%, scaling with the gear score of the item carrying it.
Forge mods that grant it
Spending one of these puts the perk on your gear instead of waiting for a roll.
Rolls on
ArmourCapeJewellery
A drop or a craft of these types can roll this perk into one of its slots.