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It generates its own energy if you need to scale up towards destroying more expensive permanents, but you can also just fire this off for and X=0 to clean up 0-mana clutter on the board

Paired with recursion engines like Myr Retriever and Scrap Trawler, it can even go infinite

Plus, some new cards, like the Etched Host Doombringer and Render Inert, help remove defense counters explicitly

Generally, simple border extensions (which I dabble in most often) should be tourney legal, but as I always say -- ask your local judge

Third, several cards in the set get better if you have the initiative

Howling Moon comes with a very low power floor of just giving a single creature +2/+2 each combat, not even trample