Well as far as I know, most 2cs seem to be pretty safe if not taken in abnormally large doses/insufflating. Alexander Shulgin (creator of almost all the 2cxs) has tested all of them numerous times. Death from 2cxs are possible, however permanent damage to any part of the body most likely will not happen unless they are taken like a coke addiction (even vitamins can be bad for you in that case). Most tryptamine RCs likely work the same way. The hallucinations/effects caused by pretty much both tryptamines (5/4--meo/aco--dmt/amt/dipt ETC.) and phenethylamines (2cxs/MDA/methylone etc.) are done so by "mimicing" (is that even a word?) serotonin. Each drug has a specific way of doing so (for example they will work at different serotonin receptor sites). This is pretty much the simplest way to explain it, because they obviously do more than just that. There are more rcs other than tryptamines/phenethylamines (for example piperazines), but you most likely won't run into them. You should be pretty safe taking rcs if you just take them at responsible doses, and don't mix specific ones with other drugs (like MAOIs or SSRIs etc., look on Erowid for which drugs not to take specifically with other rcs). And also, don't try to experiment with insanely high doses, which is possible with lsd/shrooms (this can end up with you being in the hospital/casket by the end of the night).
For what it's worth, I've taken my fair share of these rare designer drugs, and I have not noticed much of anything. Psychosis is possible, but in my opinion, the risk really isn't any greater than the risk associated with more common "everyday" psychedelics (assuming responsible use). I've notice considerably more cognitive damage from a couple days of moderate binge drinking than I do from all my years of research with these designer drugs. I think it's important to stick to those designer drugs that have been used more extensively. Most of the chemicals that have been around for many years, and that have been used by many people, have shown that they are relatively safe when used responsibly. Any problems that may occur from use have usually been observed and noted within the community, so with adequate research, you can asses the risks on your own and determine, relatively so, how safe these chemicals may be.
