This scenario was something commanded by my master as part of a day in which I was not to reach orgasm. I was to push myself up to the edge of orgasm without going over.
I laid out a towel to kneel on, and laid out the dildo, tiny candle and a glove, as commanded. Set up the computer with my master's most recent set of inspirational pictures displayed for my imaginings. Candle in glove with some lotion slid into my ass easily and enjoyably. The dildo took a little more work despite being slick. The angle I was at to keep a hand on the anal toy as well as the dildo made it a bit complex, I think.
Despite the awkwardness of rubbing my clit with one hand while keeping both toys in and manipulating them a bit and despite the position leaning forward on my knees, my excitement came up quickly. The awkwardness did seem like it would keep me from hitting that peak too quickly, and I began running a scenario that had played out earlier with my master through my mind. I could feel myself close when imagining him pulling from my hand to spray his seed across my face.
I'd managed to let the gloved toy slip out of my ass, and slipped it back in as I imagined him pressing himself into me. And that pushed me up to the edge.
Apparently my usual trick to forestall orgasm not only doesn't work when there's something in my ass, it backfires spectacularly. Trying to pull the sensation of incipient orgasm down and in triggered something of an explosion of sensation from my ass that spread instantly to everything else. I had enough time to think 'oh shit,' before being seized by one of the most amazing orgasms I've had, while still being entirely cognizant of the failure. I simply sat there for a bit, gasping in the aftermath and thoroughly unhappy at the thought of reporting it. Then I cleaned up and headed out on errands.