"
Entered the arena, killed all the three things (those hungry plants in the three corners) as always, then proceeded to the center when the boss came up normally, but was not taking any damage.
Checked the three things again, they where really dead.
Ported back to town and back to the arena, nothing changed, still invulnerable.
As a note, I (my minions) deal pure physical damage.
https://imgur.com/a/sLlesEs
Update: Just realized after going back to my Atlas, that the map was a
Shaper's Stronghold above which is still active due to completition failure, so this might cause the invulnerability to the boss. And the map was not completed before, it would have been by my first corrupted rare attempt on it.
Thanks for your report, next time you enter Infested Valley on a Stronghold, could you please walk up to the boss with your character and see if that triggers something.
My best guess is that you need to trigger some Shaper dialogue which only occurs when you get near the boss. The boss will remain invulnerable until that occurs.
If this still doesn't solve the problem, please respond.
