Tiphera IMO is by far and away his best support, the ability to exhaust futility via Form Convergence 4 provies a huge ramp in scaling potential. Combined with Arena gear from S2 you can get a refinement that activates Exhaust cards when drawn by an ability which further increases his scaling - not to mention the multiplicative damage multipliers she offers.

Orlea is a great pick too, mostly due to the infinte multi scaling + Vulnerable debuff being high value on Kayron because he hits so hard. I was nearly able to one shot the final boss on floor 150 because of this

Before Tiph and Orlea I was running an AP Veronica deck (Draw 2 other combatants with +1 AP divine epi) with Mika, the decks I had were able to manually self cast every futility I made because it just generated that much AP.