I've been looking a lot at hydrothermal vents recently, because I was making a moon with a subsurface ocean that has life in it, and I found out that Sulfur can be used as an oxidant. My question is: could a biosphere exist with Sulfur in place of Oxygen? I was thinking of disulfur, but that isn't very stable according to the research I've done. I was wondering if there is a sulfur compound that could be used in place of O2, because I think a biosphere based on sulfur instead of oxygen would be really cool. Plus, who doesn't love oddly colored skies?