Arugal Must Die
Kill Archmage Arugal and bring his head to Dalar Dawnweaver.
Kill Archmage Arugal and bring his head to Dalar Dawnweaver.

Arugal is the last boss, so this is the final hand-in of the run.
Horde: Dalar Dawnweaver in Silverpine Forest (44.2, 40.0).
Horde: Dalar Dawnweaver in Silverpine Forest (44.2, 40.0).
Seal of Sylvanas, 8,850 XP.
Arugal Must Die is a level 27 quest; you can pick it up from level 18. It takes you into Shadowfang Keep.
All Shadowfang Keep quests on one map ·Shadowfang Keep dungeon guide
Sources: Quest data from ForeverDB.net · ForeverDB: Shadowfang Keep · ForeverDB: Every dungeon quest for the level 20 to 30 dungeons · ForeverDB: Deathstalkers in Shadowfang · ForeverDB: The Orb of Soran'ruk · ForeverDB: The Book of Ur · ForeverDB: Arugal Must Die · ForeverDB: The Test of Righteousness