Shadow, Ultimate Lifeform

Menace, Haste, Vigilance
When Shadow enters the battlefield, if you cast it, create a Legendary Emerald Artifact token named
Red Chaos Emerald with "When Red Chaos Emerald enters the battlefield, lose 1 life for each other Emerald you control" and "Mobians you control get +1/+1 for each Emerald you control."

{t} an Emerald you control: Exile Shadow and return it to the battlefield.