If the egg and spider are the same upped and unupped, why not just have it be like Aflatoxin, which only generates unupped Malignant Cells?
Oh, that's just laziness on my part, they will be different when I get around to modifying the idea.
@OdinVanguard
So maybe it should be all Life? In it's currant setup anyway?
Maybe dropping the mass airborne debuff, and then giving the spiders web skill would be a better fix?
Giving the spiders themselves web would probably workout... as an alternative, you could modify it a little to something like,
"Enemy creatures lose flying status as long as you own a spider in the opposing slot."
This would allow the card to be useful in warden decks by lowering the number of elements needed to a trio instead of a quartet, but would keep the webbing from being permanent (i.e. to keep an enemy creature webbed, you have to keep a spider summoned to the opposing slot)
To make things even more interesting, you could allow the hatch ability to spawn the spider to a chosen slot on your side and swap places if the slot is occupied.
If you do want to keep things simple, you could keep the wording as is, but make the nest only last a limited number of turns:
"Lasts N turns.
All creatures lose airborne status while in play.
: Generate Egg"
You could replace N with whatever seems best for balance (probably about 2 to 4 turns would be ok).
Basically though, as long as you keep it from being able to permanently remove flying with a single card, it should be much better balanced.
Other than that, I really like the card all around.