Tentacle Attack
Inflicts damage and forwards 2 units. Nothing interesting or hard here, any healer can offset the damage done by the basic attack from the boss.
Petrify
Inflicts damage, forwards all enemies and petrifies for 3 second all your units (50% chance of activation). This skill has a 10 second cooldown.
This is the reason why this boss is annoying. Having a 50% activation on the petrify means you will have to restart until RNG is on your side and you do not get petrified.
Plague
Your whole team gets healing received reduction of 50%.
You can either run only shielders + damage reduction to deal with this or if you are high level enough, normal healers will still perform well here.
Knockback Immunity
A passive you don’t have to worry about at all since we barely have any units in the game that can move bosses.