Find the Headless Horseman's pumpkin Shrine.
The Headless Horseman is driven away, but he will return as long as Hallow's End looms. <name>, end our misery, and the insane lament of the Horseman. Face him when he is joined with his head, and destroy it!
He rests in the Forlorn Cloister of the Scarlet Monastery, in Tirisfal Glades. Find his pumpkin shrine and say this:
Your time is nigh
You felt death once
Now, know demise!
Go, <name>. And may the Light go with you.