E-121/Phi is the collective name for several robots built by Dr. Eggman based on Emerl. Dr. Eggman took the Gizoid's data and copied it to create the Phis. They are massed produced, though only fourteen are seen. The Phi robots are powered by Chaos Emerald Shards, rather than whole Chaos Emeralds.
Abilities and Differences from Emerl[]
The only physical difference between the Phi robots and Emerl is Phi's grey hue and brown eyes, as opposed to Emerl's yellow and blue. The Phis' abilities are stated to be similar to Emerl, however the Phis only use a complete moveset of one of the playable characters, making the Phis robotic, grey-scale versions of the playable characters. The majority of the Phi robots appear to be of the same intelligence level as Emerl when he had only absorbed two Emeralds, however the last two Phi models you encounter, #13 and #14, were shown to have much higher intelligence.