The creature in our fanart JSaB cursor is Acrilimus, a fish that turned into a beast upon corruption in the fan version of Just Shapes and Beats, called The Pink Corruption. It attacked Cube, though it was aimed at Cyan in Episode 2. However, it was fought and purified by Cyan shortly after. During the battle, Acrylimus floats out of the water, sending saw blades and debris flying around. After charging for a while, it summons a lot of pink particles in the air and launches a ball of large spikes downwards.
