Prontera is a city in 8-Bit Theater. All the townspeople, known as the "P-ans", have names that start with the letter "P", such as Pjoe, which is based on a 500-year old tradition.
Contrary to the fact that the game is in 8-bit, the city itself is built in 32-bit graphics. Before the Light Warriors arrived, a demon, apparently made in 16-bit, named Baphomet arrives asking for their whereabouts. With Black Mage's petty lying, the demon was fooled into thinking that the warriors were inside the town, and so he proceeded to burn and raze it to the ground.
The city is based on a city of the same name in the MMORPG Ragnarok Online. This is further referenced by Baphomet, which is a boss from the same game.