Kaer Morhen is a location in Witcher 3: Wild Hunt. Kaer Morhen is the home of the Witchers. The monster-slayers spread around the world whilst on The Path would gather here during the roughest parts of the year to regroup, share stories and have a brief rest before their work beckoned them into the wild again.
During the events of the first game the keep was attacked by an organization known as Salamandra and suffered extensive damage. During the siege - whose original purpose was the theft and acquisition of the Witchers' mutagenic formulae - Geralt and his brethren battled and defeated a host of enemy combatants, including a Frightener, and made their way to the keep's laboratory. The young Witcher accompanying Geralt, Leo, lost his life to one of The Professor's crossbow bolts, the assassin who succeded in stealing the Mutagens.
Geralt's journey will take him to Kaer Morhen once again during the events of the third game.