Tony knew she wasn't human the morning after the first time they had sex – though, truthfully, he'd had a pretty good guess for a while before that (and no, Steve, it isn't because I think no mortal woman would turn down a chance for sex with me.). JARVIS had admitted the worrying confession that he could gather no information on her vitals and that there was some sort of energy about her similar to readings off of Stephen Strange. Not real encouraging. Regardless, she was stunning in her ivory skin and electric eyes, and she hadn't killed him yet. Whoever said Tony had self-preservation instincts - well, screw it, no one ever had. So, it wasn't till the drinking challenge that he actually sat up and started paying attention again to who exactly he'd let into his life.
The whole team had been nagging him recently about how much he drank, each in their own way; Steve would level those disappointed baby blues on him, Natasha and Clint began smuggling away bottles, and Bruce would gingerly suggest another beverage choice. Only Thor didn't mention it, but he also found little wrong with scotch for breakfast, which didn't exactly reassure any of them. He supposed he should have been suspicious that she didn't nag him at all, but she had never really been one to comment on his less-than-appealing habits; when he'd disappear into his labs without food or drink, she'd either join him or vanish as well for a time, and whenever he tried to brush off his nightmares as nothing, she'd wrap her lean body around him and add to the joking armor he wore. She'd just never seemed too concerned about his self-destruction. It was refreshing – and for some reason, left a burning pang in his chest.
This was why he wasn't expecting her to sit two tumblers and a bottle of vodka (at the time, he'd laughed and asked if she couldn't think of a worse choice for shots on a sunny afternoon) on the counter between them. He was perched on one of the stools and quirked an eyebrow, but her poison green eyes had remained steady and solemn as she delivered her ultimatum: they were going to have a drinking challenge, and if she won, he would lay off the drinking-himself-into-a-stupor and would only drink responsibly. If he won, she would never again mention it. But – she'd added with a cool edge to her voice that sent shivers down his back that weren't entirely out of fear – if he lost and broke his word, she would give every bit of his tech to SHIELD, personally. And, given the fact that she'd hacked into JARVIS within their first week of dating, it wasn't really an idle threat.
He'd agreed, of course, because it was ridiculous. Sure, she'd have a drink every now and then, but it was usually one drink a day, with good reason. Tall though she was, she was slim and looked as if two beers in an hour would knock her flat. There was no reason for him to expect her to down eight shots like water and be perfectly sober by the time they'd gotten six more down and Tony's world was spinning.
"Oh, fuck," he muttered, listing sideways.
"Shh, love," she'd whispered, suddenly at his side to catch him.
Even with his weight almost entirely on her side, she moved gracefully and surely to lead him to their shared bedroom and settle him in. A few soft words and the lights had dimmed as JARVIS darkened the window.
"So, I lost?" Tony slurred, curled up on his side.
"Mm," she hummed, leaning forward to kiss his temple, "Just sleep."
He was too hazy at the moment to notice the sudden relief and calm that spread from her lips' contact out to the rest of his body. Later, he'd question why he didn't have a hangover in the same way he'd questioned her lack of bruises that first morning, but right now, her long fingers gently carding through his hair was enough to lull any suspicions into nothing.
AN: So, surprise, I don't really have experience with shots and just went with my family/internet's suggestions. I don't really know how tolerant Tony would be of shots given that he's an alcoholic, but I figured fourteen shots of vodka in pretty rapid succession would do the trick.
Also, I'm now putting this head canon into its own fic, because 'Making the Family Skeletons Dance' is pretty interconnected except for these