Immerse your Tainted Quel'Delar in the Sunwell. Speak to a Warden of the Sunwell when you are ready to enter the Sunwell Plateau.
The Sunwell and the end of Quel'Delar's exile await, <name>.
You will find Lor'themar Theron, the regent of Quel'Thalas, and Grand Magister Rommath standing within. Be wary of them and do not allow them to entrap you in their political scheming.
Instead, remain focused on your task here. Speak to a Warden of the Sunwell to enter the Sunwell Plateau. Immerse the reformed Quel'Delar in the Sunwell to complete the restoration. Show the blade to Myralion Sunblaze at Quel'Delar's Rest once it is restored.
Am I truly laying my eyes upon the weapon of Thalorien Dawnseeker? This is a wondrous day for the Sunreavers and for all sin'dorei!