I'm not that good of a drawer but with this information people could make a better version of this.
The attacks the boss can use are: water blasts that deal minimal damage and drop water ability stars, throwing ice chunks that give the ice ability and finally running to the other side of the arena leaving a trail of stars behind it. The boss needs to be hit in a brown weak spot to damage it. it is a good idea, I just need an artist to make it better. Also the boss has a resistance to the fire and water copy abilities where it takes half the damage it would normally deal but it takes double damage from the ice and leaf copy abilities.