Hydra-on-Steve gang rape where they lock his cock in a chastity cage that has spikes on the inside, so he's constantly tipping back and forth between unwanted arousal and excruciating pain. The cage is just big enough to let him get half-hard, but past that, the spikes dig in... and Steve's probably a lot bigger than it was designed for, so it's extra-painful.

Bonuses:
- Most of them are absolutely pounding his prostate, trying to force an orgasm out of him. And he's got enhanced senses and responses already: lots of oversensitivity, precome dripping all over the floor, etc.
- Eventually they give up trying to get him to come on their dicks and just wring the orgasm out of him by electrostim instead. And then a second orgasm. And then a third...