Unsurprisingly, Markos got himself into trouble after failing to pay his debt to the Cerberus. In order to appease him, Markos asked Alexios to deliver his best wine to the Cerberus as a peace offering.
Old Friends, Old Problems
Related points of interest
Objectives of Old Friends, Old Problems
1. Deliver Markos's wine to the Cerberus
It doesn't matter if you drink with him or not.
2. Return to Markos
3. Quest Completed
Rewards: Epic XP, Wine-Making Boots (Rare Legs)