Yay, MMC is making cards too!
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Anyways, this card is rather UP.
Compare to another mass AoE card like Thunderstorm.
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Sure, it doesn't hit burrowed creatures, but honestly, burrowed creatures can only really come from a few elements (Earth, Darkness, and sometimes Entropy with mutations).
I'd say to lower the cost a bit, especially on the unupped. Since it hits your side as well, you could probably lower it to 3
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, maybe even 2
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and still be fine.
EDIT: Discord replied while I was typing.
MMC was smart here and chose not to make it Earth for a reason.
If it were Earth, then you would likely be hitting your own burrowed creatures for 4 damage rather than the opponent's since Earth has the most burrowing creatures (with Graboid and Shrieker being the most used).