It is good in every list it goes in and it goes in all the lists with black mana
This requires little to no investment, and its also a powerful tutor for any missing pieces in the broken combos you might be running
Some of the more interesting cards in the game dont use your monsters, but tribute your opponents monsters
Even the base printings of Gemstone Caverns are worth around $50, so no matter what, you'll be happy to open a copy, and very, very happy if you happen to open Gemstone Caverns #51.
Since we are talking about the egg theme, I think a few good changelings are in order
You could also generate an ever-growing army of blockers via Hallowed Haunting, which switches to an offensive card once your spirits grow large enough and gain evasion