It was an unfortunate truth that Raven simply wasn't a reliable chaperon for a night of spooky celebration. Everything Tony was invited to promised to be generous with their wine and cocktail selection, and Raven was deemed entirely unsuited to the task of keeping Tony away from it as dictated by Steve and Pepper and other such wet blankets. Tony took offense to this on two levels: one, that this revelation happened showed a clear disinterest from any more appropriate parties in joining him for the evening, and two, he didn't need a chaperon, he was not twelve years old and had learned his lesson in quite a demeaning fashion in the painfully recent past. Obviously, the 'you need help, we are here to help you' lesson was somewhat more difficult to absorb.
There it was, anyway, keeping Tony from joining the rest of the living (and undead, on this night) world at the best party of the year. He stayed home, not surrounded by shamelessly scantily clad cat-girls and firemen, just one shamelessly scantily clad Raven. At least she wasn't pretending to be anything else. After the sun had gone down, they had left the lights off in the Manhattan loft and let their way be illuminated by the bright, white moon and the occasional cluster of dripping red candles, you know, for the mood, and eventually the projector that played some creepy mass murderer movie on the bare living room wall. Also, you know, for the spirit of things, Tony had dug up a possible costume design that a team had presented to him for Wanda that never got put to use and wore the scarlet, velvet cape, topped off with devil horns, to wrap both himself and Raven in on the couch where they mostly stared blankly at the wall. Horror movies just didn't illicit the same emotional response in people of their colourful history.
The result was, it was almost a relief when Tony's identicard demanded in Steve's voice, "Avengers assemble!" and Raven's cellphone started to desperately ring. There really wasn't a good chance of Halloween passing without some truly vile incident, anyway. It was in the air. They went together to Stark Tower, where Tony left Raven at the south building with a light request that she survive the night, and continued alone up the elevator to the Avengers penthouse. There was only three Avengers now-- not much of a team, and not one that Tony would be confident sending out against a threat like the zombies they were up against last year. There had to be something he could do. When he reached the war room, though, they were already standing and ready to move, and Tony could just frown in concern like an anxious mother on the sidelines.
That pissed him off a hell of a lot more than the house arrest.