Oxygen

Oxygen is an element that readily takes electrons. Iron rusts when electrons move to it. A Flame needs it to keep oxidizing. Blood uses iron to hold it for a while and let it go. A Leaf lets it out as a leftover of sugar-making.

Oxygen is not a card type. It feeds Air first, then Fire. Air is the mixture that contains it; Breath is the column made personal. This page is the oxidizer, not the lung and not the leftover flake.