Golem20 Boss fight: the power of poison (Raid Shadow Legends)

This is how I beat the Golem20 mission, using poisons!
The boss counterattacks when his HP goes down and pass some thresholds.
Howeved if the thresholds are passed with passive damage (HP Burn / Poison), the counter is not triggered.
Miscreated Monster, Occult Brawler, Tyrant Ixlimor, Septimus & Steelskull

Legends)