User blog comment:SoFaNAtiiK/Mifune's sphere/@comment-2061246-20160818015452

High Attack based Spheres would be the best if you're trying to make a Colosseum squad.

Blighted Seal (+100%) + Delusion Device (+100%) = 200% boost to Atk

Sky Harbinger (+230%) + Medblare (+50%) = 280% boost to Atk

Wicked Blade (+100%) + Vorpal Chainblades (+50%) = 150% boost to Atk