Weapon X(e)

No fear, no fear:  Xenon is here!

The Economist:  "Breathe it in:  An obscure gas improves athletes' performance"

"In particular, it increases levels of erythropoietin, also known as EPO, a hormone that encourages the formation of red blood cells. 

Xenon’s protective and EPO-boosting properties mean it is being investigated as a treatment for babies whose brains have accidentally been starved of oxygen during birth, and of adults who have had heart attacks. But it is also, in Russia, being used as a way to improve athletic performance."