earth nymph is CC and several others, even though they are ultra rare, theres a lot of people with the CC ones, and are allowed to use 6. 6 purple nymphs with no way to stop them because CC is banned seems kinda silly, and there are quite a few people with multiple purple nymphs that frequent the tourneys.
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nymph tears are snails compared to mono nymph decks, so there is no comparison there either, just saying, if you ban other CC, ban all the nymphs and replace with something else