Krirnak was a lesser orc captain from Dol Guldur.
He was the the leader of a Warg Rider unit and Taskmaster of General Burlak
He along with Burlak fought in a battle against the Wood Elves in Mirkwood and in this battle instead, of Taskmaster of Burlak, served as Lieutenant of Lombar. The Wood Elves won the battle and Burlak was shot by 4 elven arrows but Krirnak was able to escape the battle and ran to Dol Guldur.
He was finally killed when Galadriel and Celeborn attacked Dol Guldor, Galadriel Destroyed one of the Towers of Dol Guldor. Krirnak fell with the tower to his death within the pits of Dol Guldur.