Head to the right. Hit the legionary and climb the tower for the I. Drop down and head to the right. Fight or jump over the lurching legionary here. Push the chest to the right and climb it to get a coin and some Magic Potion. Head to the right and get four more coins. At the end of this area you'll find a centurion; the potion will have worn off, so hit him five times. To do this safely repeatedly walk into the bottom wall until you're right up against it, then just jump and attack. Climb the tower for two more coins, then continue right.
Defeat the legionary, then climb the tower for a coin and a key while avoiding the bird. Jump over to the right (there is a fire directly below, which will hurt you if you land on it). Push the crate to the right and jump over the fire (avoiding the bird). Do the same with the next chest. The roast boar on the other side of this fire will completely heal you, but watch out for the bird. Defeat the legionary, climb the tower for two coins, and climb the next tower for another two coins. Jump far over this one and you should land on the next chest. There are two more of the chest-fire-bird obstacle here, so solve them the same way. Another roast boar awaits you at the end, as well as the X. Climb the tower and head to the right. If you follow the lower path you can collect two throwing rocks and fight some legionaries, whereas if you bounce across the tent roofs you'll end up at a tower. Get past this tower and through the doors, and you've reached freedom.
If you've collected all three keys you'll see a poster that reads "Acrobatix and Distempa's circus now showing at Fort Compendium".