These spawn in Crucible wave 161 and another wave between 151 and 160. I don’t exactly get these. They’re not dangerous but all they do is to be as annoying as possible and ruin your streak by chain healing themselves and nearby enemies. I can’t imagine how lower damage builds can even kill these things, their heal cd is really low.
Also I think the fact that they can heal Cthonian enemies (like Cthonian bloodkeepers, not sure if these can heal them) is probably a bug - say Groble shamans only heal enemies that are beast or beastkins.