Its main feature is if it bites you your are immune to radiation for 500 seconds with the side effect of it rarely taking away stamina,health,ect, but usually it never gives you any of these, hoped this helped!-C
They can attach themselves to you even if you're wearing Tek armor, at least on Valguero. I didn't know that and thought because of my armor i'd be safe like with regular leeches. Nope, they can latch onto you no matter what you're wearing.
I don’t know if I was doing something wrong but I could never get a leech to detach by standing over a campfire I once even stood on top of one until I nearly burned to death and still nothing then i actually burned to death and still had leech on screen that’s when I realized it was on one of my Dinos and felt dumb