For my SuBuWriMo entry, The Red Sands, I've explored the idea of an ancient Pokémon world... Specifically, one similar to the Roman Empire. In the fanfiction, a man is kidnapped and forced to fight for his freedom in a Colosseum called "The Pit", similar to that of the Roman Gladiators. In his battles, he must face feral Pokémon, who are being kept against their will. These Pokémon must be chained up, locked away, etc., due to Pokéballs not having been created, yet.
The question I've come across, however, is that of which Pokémon would be appropriate for a gladiatorial setting. I've gotten the basics down, including most canine and feline-esque Pokémon.
Which Pokémon do you think would feel... "Natural", in this situation? Obviously, there are some species that would be unable to be captured, or generally impractical.
What Pokémon could you see being used as opponents in arena matches to the death? I thank you for your input, and would love to hear any ideas.