Agony is a Tier 18 Pet, hatched out of a Tier 18 Egg. It has 5 stars as it's rarity, and when you go up to the tier 18 egg, it shows to have a "??." The normal levels are above 2 million.
Golden, Rainbow, and Dark Matter
Golden: Combine 10 Agonys
Rainbow: Combine 7 Golden Agonys
Dark Matter: Combine 5 Rainbow Agonys
Golden Level is 6-8 million with 3x the amount of the normal.
Rainbow Level is 15-18 million with 5x the amount of the normal.
Dark Matter Level is 39-44 million with 15x the amount of the normal!