Mirror Bacteria is quite the terrifying prospect [1]. I'd never heard about it but the theory is that if we made a mirror bacteria, our and all other immune systems would be unable to defend against it, potentially leading to catastrophic infection of vast swathes of all life across the planet and the unavoidable death of some large percentage of all life. The benefit would be that they could be used in treatment as a chassis to carry other molecules into the body or that they could manufacture mirror-drugs that would have novel effects. Quite the addition to the torment nexus huh.

[1] https://www.science.org/doi/10.1126/science.ads9158