Im a Divemaster, so I've always looked at it like 21% Delirium means Oxygen toxicity, or that Oxygen is toxic. Basically implying that life itself is toxic. Which goes along with his whole philosophy of trust no one, everyones your brother till the rent comes due, attitude. I love Drifter. And to your point the two weapons are at odds with each other. Or maybe..just had a thought.. Maybe its called Delirium because you need Oxygen, but too much of a good thing is too much.