Playing a Fireblast in response to a Natural Balance didnt just offset the sacrifice two Mountains cost, it actually netted two mana, since the lands from Natural Balance entered the battlefield untapped
However, its in Arthurs ability that he truly shines: when played, he can give a chosen character Challenger +2 and Resist +2 (that means they get +2 Strength while Challenging and a reduction of 2 damage thats being dealt to them), plus they can also challenge Ready, not Exerted, characters on the same turn too
Cid, Timeless Artificer Cid, Timeless Artificer is an interesting build-around that I imagine comes in two flavors: You either go hard on looting, cycling, and self-mill to throw multiple copies of Cid in the graveyard, or you do some Mirror Box shenanigans
You can't divide damage dealt by a single source between them