Illestria Bladesinger at the Argent Tournament Grounds wants you to kill 10 Icecrown Scourge. You may kill Scourge in any part of Icecrown except the Bombardment.
10x Icecrown Scourge slain
The tournament is a time for testing your skills against your peers, but we must not forget that the real enemy, the Scourge, will not wait. As you hone your skills against others, so should you maintain your edge in combat against the enemy.
Travel to Icecrown and confront any of the Scourge there. I would counsel against attacking the Bombardment, [player]. It is teeming with enemies and best dealt with from the air.