Cassette Beasts

This boss is found in a cloak at the very top-left of the map on a floating isand. To get there go to the very left at the top level of Mt. Wirral, you'll see a sign pointing to the lefy. You want to be on the level above that sign, and then just jump, & glide to the left.

The boss is at level 100, so you either need to level up a lot or go for some OP builds.

One easy way of defeating her at any level is having Fungogh (evolved from Brushroom, Felix's starter). Equip it with 1x Glass Coating, 1x Paint Swipe, and then fill the rest with Random Starter's(which you can buy from the Passive move merchant to the left of the cafe).

You also want to have an Air cassette. Fill this with Pre-Emptive Strike's, don't have it equipped.

Now this requires some little luck: when the battle starts hope Fungogh get to cast Glass Coating, & then Paint Swipe, or that you have enough health left after 1 round to have painted the boss into the Glass type.

As soon as it is Glass, switch a cassette to your Air one, this will now attack the boss for as many Pre-Emptibd Strike's it has and give it 1x Resonance for each landed blow. As soon as a beast reaches 3x Resonance they die.