I've tried entropy and dark nymphs, but they don't really work well at all. Nymphs are too fragile to use without a quint, and they're so expensive for a rainbow deck, even with supernovas. If you can survive to get 14
and a quint on the nymph, you were probably going to win to begin with; otherwise, you'd have likely drawn an antimatter or two much sooner and been benefiting from it already (three chances at an antimatter, vs. 1 chance to get a nymph and 2/3 chances to get a quint). Nevermind that the 14
won't come from supernovas; you need it all from your mark and towers. Likewise, you run into problems adding a dark nymph; you need to add more cards to the deck, and the dark nymph doesn't have an analogous card you can swap it for. You also need to add a quint; one for the destroyer, one for the entropy nymph, and one for the dark nymph.
Nymphs are also a problem if you draw them off the bat; you're sitting with a card in your hand that you might not be able to play for 10 turns, which is a huge pain if you're in a low quanta situation from a bad starting hand. Drawing two permafrost shields, a nymph, and fractal is not a lot of fun.
The only nymph that I can think of that really works well with this deck is an air nymph, which just replaces the FFQ and is great for creature control, permanent protection, and EM timing. The 20 damage from the unstable gases and the 6 attack is a nice bonus, too. A death nymph might also work in place of an aflatoxin; it costs 3 more to pull off, 4 more to do it twice, and its HP is high enough to potentially survive a round of CC without a quint. I'd rather use an aflatoxin, or not use either, though.
Anyone else have success integrating nymphs to CCYB? I've got a bunch of them that I'd love to use, but I can't really seem to fit any in, other than the air nymph.