They were getting old. Too old for that nonsense. Dusk and Trixie were in their fourth decade of life, both unmarried, both childless, and both sick of their petty squabbles and pissing contests to see who was the superior mage.
The grumbles and angry remarks soon gave way to tired sighs and a desire to put all this petty nonsense behind them, so Dusk extends the olive branch: dinner in a Canterlot restaurant, all on him. Trixie accepts the offer, if only out of a sense of goodwill rather than interest, and the two meet up later that evening.
A few courses of food and more than a few glasses of wine later, the two are in a much more emotional and retrospective state, bemoaning lost and wasted years, and are hinting at suppressed emotions between the two of them. Of course, with alcohol in your system, a hypothetical mutual sexual attraction doesn't stay hypothetical for long.
Kinks: R63, foreplay, cunnilingus, anallingus, anal, light magical bondage, middle-aged regrets, rival fucking, enormous male endowments.