taultunleashed

First get a CoT mission with red damage crystals grab a healer of some kind and have them set auto heal on and stand in the red damage circle now after you take 10 mil damage you get a +10% Hp bonus

The healer can also get all the Healing badges this way too

You can of course bring lower lvls and sk them and get the advisor badges as well.

Does not exist.

Only way to get increased HP, is to get the accolades, which involve collecting several diffrent badges at high levels.