Kaon, much before the war between Decepticons and Autobots.

Before the war, Kaon was not the capital of the Decepticons. In fact, what was once the capital city of the immense Kaonite exo-empire is now a city of crime and scum.

All kinds of things happen here, but the most profitable market is the gladiator combats, especially in the Pits of Kaon, the largest and most famous arena of gladiators.

Soundwave (for reference, he is a lot buffer than Transformer Prime) is a gladiator himself, and the only one who can keep up with Megatronus.