What cards, creatures, and characters were revealed
Whenever you cast an enchantment, Tatsunari, Toad Rider will make a 3/3 legendary token that can be mutated
Magmatic Insight does this very well
Those effects are particularly good for this deck's stun and shield counters, keeping opposing creatures locked down and your own creatures safe, as well as for blitzing through the strong effects of your saga creatures
The game's basic playing pieces had been established, and Magic designers were able to experiment with what those pieces could do
Some players and playgroups dont like and dont approve of it, though, as it seems like a disrespect to the game, to its card economy, and to people who spent tons of cash to get the real cards