A new menace will be in town beginning with Onslaught, next year's large expansion. Perhaps the most sinister species ever to appear in the Magic backstory, the Vitellines are a force to be reckoned with. Rotten, greedy, and vicious, these egg-like creatures invade Otaria in force, overthrowing the Cabal and taking their place as Dominaria's premier criminal empire. I had the privilege of contributing to the creation of this species, and I'm proud to say that they're the new Phyrexians, the villains whose evil will be the central conflict behind the story of the next three or four blocks, at least.
Like the cephalids, the Vitellines were once a subservient race, created by the Shivan dragons for food and hard labor. Formed from red and green magic, they developed their unique egg-like shape from the massive heat and pressure that exists in the volcanic heart of the mountains. Ordered to constantly mine gold and gems for the greedy dragons, they quickly developed so much bitterness towards the dragons, and the unfair world at large, that they longed to strike back. Only Yawgmoth and the Apocalypse could break the dragons' hold on them; when it did, the Vitellines took revenge in force, slaying many dragons in a fierce bid for freedom, and swearing vengeance on all of Dominaria for their long years of servitude.
Linked here is a complete, exhaustive write-up I've been developing for the Vitellines, my extensive notes for their culture, ecology, and history that really make them into a rich, textured species I believe players will be talking about for years to come. So go and take a look; I know you'll gain a new appreciation for the Vitellines once you see what they're really all about!