The thing can still block with its full toughness and use abilities, so you dont even get rid of a whole card with it on some creatures
You would need a cycle of 20 to do all variants of it as it is not symmetrical in how it treats the colours it fixes, like if you were to do a full cycle of the Tainted lands from Torment
Just cast it before youve played your land for the turn, and at least you get a Clue out of the deal when they kill it
Building a deckwith authentic cardsis part of the entry fee into tournament Magic , and that's perfect fine
This aspect of deckbuilding with emerald will likely be hard to grasp for newer players, but will ultimately reward those who put the time into finding the right balance
At the beginning of your end step, if a creature died under an opponent's control this turn, create a Treasure token