They’re mostly all synthetics derived from amphetamine class of drugs like MDMA.
2CE. 2CB. 2CI. Etc. and countless others. No one taking them know what it truly is.
They are dangerous. And more ubiquitous than LSD-25.
You can never be sure what you’re getting. You can OD and have a psychotic episode.
I do not classify them as therapeutic psychedelics, and always advise against.
If you ever take a tab of LSD and it’s bitter or metallic, or anything but absolutely flavorless or just paper, do not take. Spit it out.