Sadly a much worse Nerubian Egg. It's still good, but not nearly as useful. It dies to less trades / board clears, and 3 mana vs 2 mana makes all the difference between playing something extra and making a commitment. It's basically 50% more expensive for a mere +1/+1. On the plus side, there are way more things that deal 4 damage than 5. Still, while it might see some play, I don't think it will see as much play as Nerubian Egg did.
Spiritsinger Umbra (4) > Devilsaur Egg (3) > Mirage Caller (3) to copy an Egg - This would put a 3/4, 0/3, 5/5, 2/3, 1/1, and a 5/5 on the board for a total of 6 minions with 16/21 in stats with another two minions both with 5/5 being summoned from deathrattles if the Eggs are not silenced.