Reach of the Damned is a silver sword in The Witcher 3: Wild Hunt.
It can only be found as random loot inside caves in Velen and Skellige, and from guarded treasures. One guarded treasure location known to spawn it (although it only guarantees a relic item and not this particular sword) is south of the Ruined Watchtower in Kaer Morhen, guarded by a Leshen.