OOC: So I've decided to write character essays. Originally, it was going to be one essay, but there's way too many topics I want to address, so it's going to be many shorter essays, or at least, that's the plan.
Derek and monogamy.
Derek was not remotely monogamous for most of his life. He has had four steady girlfriends now, counting Toxin, and otherwise, has simply flitted from easy lay to easy lay. That was what put him with Trisha Collins, the girl whose rape and murder wound up sending Derek unfairly to prison. In prison, he was largely celebate, being uninterested in homosexual sex for purposes of sexual release. (Purposes of domination were something else.)
Upon release from prison, Derek was naturally more than a little horny. He was also more than a little rusty. He was looking for Magneto, and stirred the pot enough for Mr. Magnet to find him within a month. So he never quite got himself around to arranging a one night stand for himself, between his parole job at the Sweet Basil and his searchings for purpose and his readjustments to real life. So he didn't get laid until he and Toxin finally got together. Because of that, he places some special value on the nookie he has received from her.
He is also making a concerted effort to stay true to Toxin. She's beautiful, she's rich, she's talented, she's intelligent, she's fun, she's compatible, she's a mutant, she's powerful in the Brotherhood. So she's definitely a 'catch'. Truthfully, any woman in the Brotherhood he hooked up with, he'd be prepared to treat very seriously (even Sabella, though he wouldn't expect she'd want to be serious.) If he and Toxin do break up, he'll want to go back to NYC long enough to bang the hell out of half a dozen fully human trollops. In any case, since it's been eight years since he had /any/ kind of a relationship, he's making a concerted effort to turn over a new leaf; he's no longer a college kid. It does take a bit of an effort not to want to stray, but he thinks it's the right way to go.
More on Toxin in a later essay! (Possibly in more than one; she's a major figure in his life.)