In the Karazhan Raid:
www.wowhead.com
in the Chess event:
www.wowhead.com
It cannot be activated, since the pieces are neither as a player nor in gm. If this event cannot be completed, a door cannot be opened to continue the raid.
I leave reference video:
Karazhan
Karazhan is an abandoned ancient tower located in Deadwind Pass. Karazhan is notable for its famous occupant, the last Guardian of Tirisfal, Medivh.
www.wowhead.com
Echo of Medivh
Echo of Medivh is an Elite NPC that can be found in Karazhan. In the NPCs category. Added in World of Warcraft: The Burning Crusade. Always up to date.
www.wowhead.com
I leave reference video:
