Level 20

This is the second boss you will fight. It is like Level 10 but with Terror Dactyls instead.

Strategy
The first wave of monsters have monstrously high power (higher than the Koopigg miniboss!). They thankfully have low health, but it doesn't end there. They have Life Steal moves which heal them depending on the damage they do. Once you are done with those, you get introduced to the boss, who has double the power, 4 times the health and a little bit more speed than the Koopigg miniboss. His attacks are pretty much insta-kill, so completing this level will be very hard.

Strategy 1 (no healing)
Monsters: Primigenius, Bonbon, Freetle

Moves: Primigenius must at least have either Decrepit Rush or Venerable Stomp. Freetle needs Fire Dart and Bonbon needs Sand Tornado

What to do:

Bonbon and Freetle will slowly kill off the enemy team. Make sure that by the team the enemy team is killed, Primigenius has Regeneration applied from Decrepit Rush. If he doesn't have the move, then it will make the run slightly harder. The boss will then appear. He will do either a Life steal move first (for some reason) or a simple damage move. Primigenius must stun him with Venerable Stomp and Freetle must burn him. Bonbon must blind Terror Dactyl so that he has a lower chance of healing himself. Now just wait for the burn to finish off Terror Dactyl

Strategy 2 (no Primigenius)
Monsters: Freetle, Bonbon, Tarzape

Moves: The same as above. Tarzape must have Fresh Respite and Fur Punch.

What to do:

Do the first half as said in Strategy 1. Make sure that your team is near full health by Tarzape's healing. Then the boss appears. This time instead of stunning the boss, you majorly lower his accuracy by applying Blind and Daze by Bonbon and Tarzape respectively. Then Freetle burns him and it is pretty straightforward from here.