We got into MDMA like 4 years ago just pre COVID. We then had sexy roll parties w friends during Covid at our house (none of have kids) and I told my GF when she and I would roll and share fantasies always thought if would be hot if anything happened w/ our close friends.
One night at a house roll party in got down to three couples that included us (5 of the 6 were still up the wife of one friend was tired and went to bed). We all wind up laying on soft blankets in a cuddle puddle on floor. Previous nights we had all been touchy feely, kissing each others partners, massages, etc (if you've rolled you get it). This specific night we all were close to taking next and 1st step with friends we’ve had for years and had never done anything, had played some sexy jenga and other games.
Well it heats up while on the floor as someone starts kissing a different partner. The solo guy feels the vibe and gets up to clear with his wife that he could mess around (she the next day said she was too tired and nauseous; she'd catch up the next time) and she said cool to proceed.

My GF starts blowing me and my guy friend is on the side (his wife was who had gone to bed and who was now solo). Our other couple friends were next to us on the other side fucking with my friend’s wife riding him. She grabs my hand and puts it out her boob and squeezes my hand to grip harder. I realize during the blowjob that my GF was jerking off my solo friend next to us once I heard him sighing (my GF next day said he felt bad he was solo). The girl ride her husband is moaning loudly, my GF is blowing me and our solo friend (with the sleeping wife) now softly moaning while getting a handjob.
Solo friend while I am getting the GF blowjob then during this moves around and fingers my GF from behind. She gets super wet and it is super hot. The wife riding her husband finishes in loud fashion; none of the guys finish (an MDMA side effect...) and we all decide to go to sleep as it's late.
Since we had never discussed it/done it (even thought I think separately we had all talked about it with our respective partners), for like a week my friend asks me if all is okay as does my GF separately and I say yes. However internally it did take me a week to process it but later realized how hot iit was hot and something I always wanted to happen (and the memory has made the "spank bank" a few times...)!
2 months later the wife that was sleeping now is not, we wind up in a 4some with them (soft swap) and then happened multiple times over a 2 year period. So many amazing, hot, steamy events that I'll never forget until I die! Sadly they just had a baby and move away so that has taken a pause but now we dabble a bit with other couples and expect in a few years they'll be ready to go at it again.

Hands down no regrets as long as you are open minded about it. Only wish it had happened sooner!