How do you beat stage 12 on monster squad mansion of madness have

Have team of 20:
Normal:
-pentacorn (max 6 star)
-katadon (max 6 star)
-ghoulsmash (max 6 star)
-mew celest (max 4star)
-octoqueen (max 5 star)
Water:
-jeliking (max 6 star)
-whalduke (max 5 star)
-beetortle (max 5 star)
-freez (max 4 star)
- coupion (max 4 star)
Fire:
-talmag (max 5 star)
-magroon (max 5 star)
-karios (max 5 star)
-shade (max 4 star)
- fire bat (max 5 star)
Earth:
-wynocheros (max 6 star)
-darkmonk (max 5 star)
-megabomba (max 4 star)
-popochy (max 4 star)
-kroko (max 4 star)

All of the 20 all have +5 and lvl 30 all the 6-star and some five star have runes equipped as well
Can't figure it out I took my jeliking,pentacorn,katadon,ghoulsmash, and whalduke and completed stages 1-11 with just that team no deaths hp full.
Then the final boss I used full earth team (k.o) then full fire team (k.o) and then used the water team which brought boss down to 3/4 life because she kept healing....
Finally got my main team in using katadon as lead for his shield and mew healing all , I got her life down to 2% and then she healed so much! Got her back down to 10% but by then she was way to strong and I died. :,(