The Tier 17 Egg was added in Update 9.
This egg costs 26,500,000 Moon Coins.
Opening the egg gives you variety of different Dominus pets. These pets include:
Note: Rarity is based off of the pop-up menu when going near an egg/present. The "??" Rarity is also known as the "Godly" Rarity, since pets/hats in this category are much more challenging to obtain.