Level 15

This is the second miniboss you will be fighting. The Koopigg has 10 times the health, twice the speed and little bit more power than most of the rares in previous levels.

Strategy
The boss has very high health and speed, but his power is only slightly higher than what you have fought. The most threatening move he can do is Thunder God, which will do 209 damage! One way to put this simply, do NOT use water monsters.

Strategy 1
Monsters: Bonbon, Tarzape, Freetle

Moves: Freetle must have Fire Dart, Bonbon must have Sand Tornado and Tarzape must have Fresh Respite

What to do:

Koopigg will do some damage with Thunder God, but thankfully all the monsters on the aforesaid team are pretty tanky. Bonbon must do Sand Tornado for heavy earth damage and Blind, which will lower Koopigg's accuracy. Freetle has to do Fire Dart as a chance to burn Koopigg, chipping off his health. If Bonbon needs to attack again, make sure he recharges when Sand Tornado is in cooldown and Bonbon has less than 80 stamina left, as Sand Tornado costs 40 stamina. Thankfully, Bonbon has the Energized trait, helping him with that high stamina cost. Tarzape is there to heal your team.

Strategy 2 (Self-killing cheese)
Monsters: Bonbon, Tarzape, a third Thunder monster

Moves: The important thing is that Tarzape can heal his team. That's it

What to do:

Koopigg's special involves killing himself, and the damage will only target one of your teammates, so you can use this to your advantage. Tarzape is needed to heal your teammates. Just let Koopigg attack until he decides to do his special. From here he literally plays himself. Let Tarzape heal your teammates when they are low in health. Do note that this process might take time.