Here is the list of currently revealed characters:

Oxygen

Oxygen is a gaseous fighter. It utilizes small bubbles that form into legs so that it may run and jump across the screen with amazing speed and agility. It uses its fists to knock its enemies back and forth across that screen, and every now and then, nails an enemy with its leg bubbles in an explosive fashion. Oxygen is a fun loving character, but is also a bit of a hot head. Get it too hyped up, and it will burst into flames, singing all its foes!

Carbon

Carbon is nonmetallic brawler with a burning passion for the art of the fight. Carbon hits hard, jumps high, and launches small fire balls at its enemies. When Carbon charges enough energy, it pressurizes itself, turning into solid diamond, before launching into the sky and crunching those below it with atomic force.