User blog comment:Jord aaan/Challenge Arena/@comment-24570336-20151024094956/@comment-24570336-20151025024313

Your league determines the rarity of units you bring in, and there is a leverage for the strength of your squad. Make your squad too strong and your opponent can start first, possibly OTK your squad regardless of what your setup have.

Once again, the units you bring into Challenge Arena will all be of use, as long as it satisfy the league requirements. Bring in weaker units and win, and you can possibly earn higher points at very similar risks compared to stronger units. The rule changes every battle so you need a variety of units that can fit in efficiently for any rule that comes.