The Battle for Athens - Act 1 Story Quest
The Battle for Athens is the fifth main quest in Act 1 of Titan Quest and it starts by speaking with Feiyan in the Pythian Caves whom you meet immediately after you defeat the 3 Gorgon Queens. Speaking with Feiyan will complete the previous quest The Source of the Monsters and begin this one.
All you need to do for this quest is to travel through a few areas and then speak with Leonidas outside of the Athens front gate. On the way to Athens you will pass by two Side Quests as well as one of the most well known Legendary Farming Locations.
Side Quests In Area:
Trapped in the Ruins (Kephisos Valley)
Spartans Lost (Kephisos Valley)
In the same area that the Spartans Lost quest takes place you'll find the Lernean Hydra (Legendary Difficulty Only). This monster is one of the more popular farming locations on Legendary. For more information about this farming location check out my Lernean Hydra Farming Location Guide.
Once you've made it to Athens speak with Leonidas at the front gate (pictured above) to complete this quest as well as start the next one, The Order of Prometheus.