As with all the other new areas, there are a few prerequisites to be able to begin the quests to opening Epona in southern Harvest Counties.
As of right now (December 2015) it unlocks about halfway through level 16, once you have completed all of the following story arcs:
- Help Helga the German tourist with their summer house. [Day 55]
- Infiltrate the Jarlaheim G.E.D. office and sneak internal reports out to Herman at Jorvik Stables. [Day 69]
- Reach Friendly reputation status with Jarlaheim G.E.D. office through daily quests. [available after previously listed quests]
- Have unlocked Valley of the Hidden Dinosaur and helped Nic Stoneground explore the area. [Day 92]
Once all of these quests have been completed, you will receive a pop-up quest in the form of a text message from Herman, asking you to visit him at his home in Jorvik Stables.