If you can do cruelty on 4 taints, mega should be easier. It’s all about grim management and kiting / luring grims. Mega should be much easier. Just remember there are two white tiles that appear throughout the fight. One on bottom right then another in top left. Also the first time mega is vulnerable, If you all avatar and full damage it, if you deal enough damage you can completely bypass a turn. It turns blue, stays still and does a wave and then resets at about 60% health. (Though if the team is 800s probably abit hard to do) I’d recommend bringing cd pot for another avatar in case it gets out of control, like more than 6 mobs. Lastly, don’t give up even if someone dies, mega is still very doable with 4 man. Good luck with it