Timestops definitely. Pay attention to her mana level before using the next one. Always use another timestop if she’s about 60% filled or so. Maybe 75%.
Yes, time stops instead of tornadoes. And if I see correctly, you have two healers in your team (Vivica + Boldtusk). I would swap one of them for a “sniper” hero - possibly Caedmon. After you are though the mobs, fire dragons + bombs, fire your heroe’s specials and after that use time stops to prevent the bosses (especially MN) from firing their specials.
As others have said, focus down Mother North first. Use time stops to prevent her using her special, and throw all your bombs too. You can also charge up Chao’s special with tornados and super Mana potions and fire at Mother North to drain some of her mana while whittling down her health. I did it with only 4* heroes but it took five time stops, five tornados, five dragon attacks and five super mana potions. Good luck!
Tornadoes + time stops + bombs + healing potions (just in case)
Fill up your mana in previous stage and take control of the situation from the beginning in last round, fire everything you have and don’t let them use their specials!
I was able to successfully clear advance 24 with the team and items below. It was a long battle but in the end i used all my items and all my heroes survived. Luckily I didnt have to use 75 gems to res.
Mother North was able to pull off 1 special but luckily I was able to recover.
Thanks again for all the advice. I swapped boldtusk out for caedman and his fast snipping helped out alot.
Hopefully this helps out anyone trying to finish the event.