I agree with putting in Urborg, Tomb of Yawgmoth.
Also, maybe a small amount more of removal like bile blight or dark betrayal.
I don't know if I just didn't pick up on it, but I also didn't really see a theme that you were focusing on in the deck. I saw the festering newt, bogbrew, and cauldron combo, but I didn't see how some of the other cards were fitting into it, but it could have just been me.
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