You can tether at any time, but you only gain health if they are weakened first. The boss can also be tethered once its minions are defeated.
I think the tether is a little bit overpowered then? I could just drag them all off the stage one by one.
How did you manage to stay alive that long without absorbing any of them though?
The slightly pink/purple ones give me energy anyway. Could also be a bug?
Oh indeed, must be a bug then. Thanks for bringing it up! Definitely an oversight.