Speaking of cards likely to stick around in the format, Excalibur, Sword of Eden seems pretty cracked from my testing so far
If were to make an educated guess, once players have collected all six stones, and placing it within the Gauntlet, unlocking a special win condition would be the most natural outcome
Finally we have Rage Reflection and Dictate of the Twin Gods that are included mostly for the flavour, but in conjunction these cards will melt our opponents as together they quadruple the damage our creatures could deal
Play more of both, be happy
Another interesting thing to exploit with the mechanic is to convert 3/1 fliers into 4/2s (Brazen Borrower, Elite Spellbinder) since they'll be able to get the counter with 1 toughness
A lot of players sleeve up the cards they get out of a box and then recreate the booster packs