Breathing Nitrogen

Vohra, Vreka, and Bayvak all breathe nitrogen. They evolved from bacteria that absorbed nitrogen and converted it into energy. Rather than two large lungs, they have four small lungs that work independently of one another. Due to how common nitrogen is, this has allowed them to expand and colonize many worlds normally unsuitable for other sentient races.

Retha breath a mixture of nitrogen and oxygen. They have three lungs, the two outer lungs using nitrogren and the central lung using oxygen. This enables them to convert energy more efficiently, making them deceptively fast, despite their large size.