The scene was set at the top of an active volcano. Quite an inconvenient battle environment for most people, but nothing major for the two in question.
This place was just barely past the Dragon Lord's manor. That place remained at the foot of this volcano because the terrifying flames were enough to burn even an expert in Nonexistence.
These flames were the basis of the Dragon Lord's power, and they were a perfect tool to use if one wanted to see one's enemy suffer.
Maybe that was why Chaos waited here.
It wasn't difficult for Damien to find him after leaving the containment unit. He made his aura clear to the only person who recognized his existence, calling him to their battleground in something like a show of courtesy.
He waited at the top of that volcano for Damien to arrive, and without time to stall, Damien did exactly that.