One of the biggest reasons why people never used Puffer Fish is
because of its 2 attack! Why use a creature in an upped format (solo play and some PvP) if most of the shields you face completely nullify it? Even Permafrost Shield completely shuts it down, and that's coming from the same element. Puffer Fish is perfectly fine as a 3 attack creature. I do think that it should be a 3|4 instead of a 3|5, because then it could be eaten by a 0|5 Otyugh. Because it is poisonous, it is still immensely threatening to the Otyugh's owner, because once the Otyugh devours one Puffer Fish, it will most likely die soon, especially if there are Physalias and more Puffer Fish on the way.
@Zanz: The Wyrm's skill cost reduction was just wishful thinking on my part. I understand why its skill cost is
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and it's still a fine creature. Maybe there should be another mid-ranged creature for Air...