Kor'kron Vanguards are orcs located at the Kor'kron Vanguard in Dragonblight. It can be presumed they were among the forces who accompanied Saurfang the Younger in the Battle of the Wrathgate.
After a player completes Return To Angrathar (Horde), Kor'kron Vanguard will phase out of existence for that player and will no longer be available.