Serket can be completely owned with wings, because he has no flying creatures. None of those FGs have any kind of permanent removal, so dimensional shields would be pretty strong as well. They also all use poison, so purify is strong against all three. I'd probably try to either make a duo with two of air/aether/water, or else a rainbow incorporating wings and/or dimensional shield, sundials, and other stall elements like that, while finding a slow but difficult to stop win condition. (quinted blue nymph, phase dragons, quinted steam machine or firefly queen, weapons, etc, would all be difficult to deal with, although steam machine would struggle with morte's bone wall, but a shard of wisdom gets around that; firefly queen's flies chew up bonewalls pretty quickly) I have some unupped FG counters in my signature; you could take a look at those and get some ideas for some FG-specific counters; you'd have to modify them to work against more than one FG, but it would give you a place to start. I also have a link to upgraded FG counters in about the 2nd or 3rd post of the thread in my signature, which should give a few more ideas.