The primordial bulwark treasure does not seem to trigger in anomoly mode with the anomoly that heroes take double damage if the initial damage is less than the heroes health. I came accross this in my run when I was at 7/8 bosses and lost against Illidara Sunsdawn. I was at 22 health and got attacked by a 14 attack minion while primordial bulwark secret was still in play but instead of making it me immune and dealing 40* (20 damage doubled due to anomoly) to her and letting me win, it didn’t activate and I just died. This was probably due to the damage being less than my health when the initial calculation took place which did not meet the requirements to trigger the secret but then the damge was doubled and the trigger for the secret was not checked again so I just died. I hope this helps you resolve the issue. Thank you
From the known issues thread:
Primordial Bulwark does not activate if the active run has Anomaly - In the Face.