Pestilence

The Missing Rider
You sense a presence lurking in the shadows. A heavy pressure pushes down on your shoulders. It intensifies as the missing rider walks closer. They didn't expect to be found so easily. Back luck for them. For you? Who knows.

A hand, fingers obscured by a heavy sleep, reaches out to you. Pestilence will speak.

After completing the 'Famine's Revelation' quest:

The Missing Rider
The missing rider is nowhere to be found. You can tell that's the case because it's easy to breath. Do you remember the vow you made? Even if you don't, Pestilence will.

Would you like to reminisce on your encounter? If so, speak.

Locations: Reap Finals

Note: Appears after completing the 'Take Ill' quest.

Thanks to Sammzy.