changeling mtg cards War-Spike [Modern Masters] sacrifice it unless you exile another creature you control Changeling Hero [Lorwyn]

But Cavern of Souls is the only one that has the clause that makes your creature spell uncounterable

At that point, youre talking about an entire strategy revolving around infinite resourcessomething that should already fall under the umbrella of a Rule 0 discussion

High impact

It has some built-in help by gaining life whenever you cast a white spell, but Im thinking in bigger terms

1 | Bludgeon Brawl $0.40 Mana Value: 2R Rarity: Rare Card Text: Each noncreature, non-Equipment artifact is an Equipment with equip X and Equipped creature gets +X/+0, where X is that artifacts mana value

Best Outlaw Cards Lets look at the best outlaw cards, and by that I mean cards that specifically interact with outlaw creatures, not just outlaws themselves