The player has to engage 2 Pyropigs. Each enemy's stats are shown below.
First, attack every turn that you like, but when the Pyropigs are about to attack, protect all birds by Red's secondary skill and use Chuck's secondary skill on Red or himself. When the Rage Chili is full, drag it on Red if there are two Pyropigs but if one Pyropig is almost out of health or there is one Pyropig, drag it on Chuck if there are two Pyropigs and they're not out of health yet. Repeat this over until you win or lose.
The Pyropigs now can increase their power by 25% percent, so Red's Guardian class and Chuck's Lightning Bird class will indeed come in handy. Red can lower their power with Overpower, and Chuck's Energy Drain can dispel the power increase.