Went to my first festival, my girlfriend was by guide and wasn't used to doing drugs with newbs. Took a good amount of mdma and a double dose if LSD with no experience in either. Who knows what was actually in the mdma, as you say.
I was gone in ways that are hard to describe. There were moments I thought I would die (and accepted it! Imagine!), moments I thought I was special and unique, and moments where I felt like a grain of sand in the desert. After the mdma started to taper off, I was totally unresponsive to the outside world and ended up at the medical tent for a while, definitely not the experience people look for.
My girlfriend still apologies to me about it sometimes, but man. What a fuckin' ride.