E-121 Phi

E-121 Phi (φ) (ファイ Fai) is an Emerl-based robot made by Doctor Eggman. Dr. Eggman took Emerl's data and copied it as stated in Rouge's story mode. The Phi robots are powered by Chaos Emerald Shards, rather than whole Chaos Emeralds.

Abilities and Differences from Emerl
The only physical difference between Phi and Emerl is Phi's grey hue and brown eyes, as opposed to Emerl's yellow and blue. The Phi's ability to copy attacks is identical to that of Emerl, but since the ability is only powered by Chaos Emerald Shards, as a whole it is weaker than Emerl's. At first they don't have much vocabulary, repeating one word while speaking, such as "Located! Located!" But later, they're able to speak more fluently, such as "Captured! I will capture you! I will capture you for Dr. Eggman!" Unlike Emerl, Phi has all the abilities of one character, instead of a combination of skills mixed up together. That means no Ultimate skills and no Combo skills.

Trivia

 * Phi is the twenty-first letter of the Greek alphabet. However, since the first E-100 Series robot was designated E-100 (as in the Greek Alphabet, Alpha is counted as 0, then Beta is counted as 1 and so on), the Phi robots should be designated E-120. E-121 should be Chi, and E-122 should be Psi.
 * Phi has a lower serial number than E-123 Omega, meaning that it was created earlier. However, Sonic Battle takes place after Omega's first appearance (in Sonic Heroes), as Rouge comments on Gamma and Omega looking similar. This might mean that Eggman was working on Phi before Omega, but he finished building Omega quicker. Eggman may also have saved the Phi model robots for a later purpose, such as collecting Emerl.
 * Phi is the only E-series robot to have multiple versions of itself.