Edit: There is a slight pause on my work on this as I am staying OUT of the arena until the new dragon arrives - I now have two Sweet Tooth and don't need more clutter in storage.
As many of you know, I've been curious about the difference in strike types in the arena and at least one other player has a similar interest: you know who you are but I have forgotten your name, I hope you see this.
I have started taking notes. My first observation was that Splatter, a Rainbow/Red, uses blue magic. I was up against Lunar Rainbow and noticed blue is weak against Rainbow type.
I've noticed that when I use Champion against Rainbow, invariably the magic strike is weak, but the bash takes out the opponent. I just fought Triple Rainbow and it dawned on me. Warrior Prince uses black magic. Black as a colour is weak against Rainbow, but the Champion type is strong against Rainbow. I won't bother using magic against a Rainbow type again when using Warrior Prince. Do all champs use black magic? He is the only one I've used in the Arena, so I can't compare. My Gilded Knight is going to level 10 today, but I don't think I've used him before.
I think the type of magic is important.
I would be interested in any research contributions from other players. Who else is interested in this investigation?