I just got the game and am playing the single player campaign to learn the ropes, I am playing as Necron and am trying to eliminate the Sisters, I have blown up everything on the map and then I get a new mission to destroy the statues of the shrines of the living saints, there was something about them being invinceable and now I believe it, I can't seem to do any damage to the statues or the living saints that appear, I assume there is a trick to this, but so far it has eluded me.
By the way, note when you're playing as Necrons, it is possible to get a shrine max HP below zero with Pariahs. Just try to make sure when you're attacking a shrine, Saint Anais is not there to join the fun.
Anyway, if the negative HP bug does occur, just delete the Pariah squad.
“Tragedy is when I cut my finger. Comedy is when you fall in an open sewer and die.” — Mel Brooks