It has three forms, and is known as UB-0 Black in the anime
It still makes use of Urzatron to power out big spells, but instead of focusing on ramping as efficiently as possible, it plays Eldrazi Temple and other utility colorless lands to play a more rounded curve of creatures
An uncounterable 15/15 with flying, protection from colored spells, and annihilator 6, upon entering the battlefield, Emrakul's controller takes an extra turn after this one
You wont be as incentivized to play the remaining enchantment removal like Seal Away and Ixalans Binding with Cleansing Nova in your deck, but theres no harm in having the versatility to destroy all artifacts and enchantments as well if thats necessary
Since they can always bounce themselves, they give you a starting place for repeated (1) ETBs, and (2) creature casts
In my own cube, I don't have access to one, which is why I use Ulamog, the Ceaseless Hunger in its place