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Sonic Wiki Zone
Sonic Wiki Zone

Detected! You will be captured! I will capture you for Dr. Eggman!

— E-121 Phi, Sonic Battle[1]

E-121 (E-121 Í-Wan-Tsu-Wan?), codenamed Φ (ファイ Fai?), is a character that appears in the Sonic the Hedgehog series. It was a mass-produced, E-Series robot model created by Dr. Eggman that was based on Emerl. During the Emerl incident, the Phis were sent by the doctor to get Emerl, who was with Sonic and his friends, though these attempts failed. At least fourteen models have been produced, all of which were powered by Chaos Emerald shards.



Described as ugly, the Phis were based on Emerl;[2] as such, they were humanoid robots. They possessed five-fingered hands and feet in the shape of shoes. They had spherical joints as shoulders and pelvis-legs, as well as a relatively thick armor around their forearms and lower legs, thick kneecaps, and some kind of jetpack on their back. On their chest, they had three beige circles. Lastly, they possessed a spherical head with a mouth plate, olive green eyes, caps for ears, and a curved horn with a closed eye on their forehead. The only difference the Phis had from Emerl was their colors; instead of being beige and light brown, they were colored in different shades of gray.


In Sonic Battle, at least fourteen Phi models were created by Dr. Eggman with the raw data he obtained from the Gizoid before getting disposed of him. The doctor also crushed a Chaos Emerald and used its shards' energy to power his new robots, while programming them to go find more Emeralds.[2]

You've got a friend in phi

Rouge confronting Phi #1, from Sonic Battle.

The first Phi was deployed by Eggman in Central City to fight against Rouge, but she effortlessly destroyed it and got its Emerald shard. A second model would fight against Sonic near Tails' house in Emerald Town three days later before running away, and another one would appear to encounter the Gizoid, now known as "Emerl", to later run away as well.

Sometime later, three other Phis would receive orders from Eggman to trap Emerl and bring him to the doctor. They would show up in Night Babylon and cause chaos there. Two Phis in particular would be fought and destroyed by Knuckles and Emerl at Club "Rouge", who claimed their respective Emerald shards, as well as one Rouge had. Afterwards, in Emerald Beach, the fourth Phi produced was deployed by Eggman to battle Knuckles and Emerl but failed. Soon after, the fifth Phi fought against the duo, but to no avail.

Not too long after, two Phis fought against Emerl and Amy in Emerald Beach, but the heroes destroyed them and claimed their Emerald shards. Later on, two more Phis encountered the duo in Night Babylon. Like before though, they were defeated and dropped their shards.

Afterwards, Eggman sent the eleventh Phi to fight against Emerl and Cream in Central City, but soon changed his mind and decided to send the two to Gimme Shelter. There, he tasked the eleventh, twelfth, thirteenth, and fourteenth Phis, as well as Chaos Gamma, with watching over the duo and preventing them from escaping. However, the Phis were destroyed.

In gameplay, the Phis appear in certain points of Sonic's, Rouge's, Knuckles', Amy's, and Cream's Episodes to fight against these characters and/or Emerl and progress with the storyline. They also appear in secondary, optional battles in all of these Episodes, as well as Tails'. During battles, the Phis have the move set of every playable character, except Chaos. Unlike other characters, however, the Phis do not award the player any moves, but they do grant them Skill Points based on their performance in the fight.


The Phis were mindless robots, who carried out Dr. Eggman's orders without question. They also showed far less sentience than their template, Emerl, did, possessing limited speech and being only able to say a few words, including "Roger",[3] "Located",[4] and "Retreat".[5] That said, though, the thirteenth and fourteenth Phis showed more sentience and could even call others of themselves for backup.[1][6] It should also be noted that these robots were very hostile, resorting to violence immediately after locating their target.[4] However, if they were heavily damaged, they would resort to escaping.[5]

Powers and abilities[]

As members of the E-Series, the Phis were very advanced robots that was developed to advance weaponry.[7]

Perhaps the most noticeable feature of the Phis was their ability to copy others' moves and use them as their own, much like Emerl. Unlike Emerl however, they could not mix moves from different users, and were only restricted to a single move set. For example, only certain Phis were able to use Sonic's moves, including his supersonic speed, but could not use abilities from other persons such as Tails, which were restricted to other Phis.





  • Phi is the twenty-first letter of the Greek alphabet. However, since the first E-100 Series robot was designated E-100, the Phi robots should be designated E-120, and E-121 should be Chi.
  • 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.
  • Rouge's move set is the one most frequently used by the Phis, as it is used by three separate models during story-specific events.
  • Phis are never encountered in Holy Summit.
  • The theme of the Phis, which is also Emerl's theme and the music for the Colosseum arena, was remixed as the music for Nonaggression in Sonic Advance 3.






  1. 1.0 1.1 Sonic Team (27 February 2004). Sonic Battle. Game Boy Advance. Sega. Area/level: Gimme Shelter (Cream's Episode). "Phi #14: Detected! You will be captured! I will capture you for Dr. Eggman!"
  2. 2.0 2.1 Sonic Team (27 February 2004). Sonic Battle. Game Boy Advance. Sega. Area/level: Central City (Rouge's Episode). "Rouge: You know, you're wanted by the government for questioning about a certain item. / Eggman: Hmph! I tossed that piece of junk at the beach already! / Rouge: What? You threw it away? / Eggman: The world's deadliest weapon? What a joke! That worthless thing can't even listen to basic instructions! It's probably making friends with the crabs right about now! / Rouge: With crabs? / Eggman: I used the raw data from that robot to build a much better robot. Its name is E121 'Phi'! / Phi: ... ... ... / Rouge: What an ugly contraption. / Eggman: These guys are powered by pieces of the 'Chaos Emerald.' I created 'Phi' by using Emerald shards from the Chaos Emerald I crushed! / Rouge: You created this... / Eggman: And I programmed them to collect all 7 'Chaos Emeralds'! In no time, I should have all 7 'Chaos Emeralds...'"
  3. Sonic Team (27 February 2004). Sonic Battle. Game Boy Advance. Sega. Cutscene: Intro (Knuckles' Episode). "Eggman: Hah hah hah!! Go!! Go, my painful 'Phi' robots! Bring the Gizoid back to me! / Phi #1: Roger! / Phi #2: Roger! / Phi #3: Roger!"
  4. 4.0 4.1 Sonic Team (27 February 2004). Sonic Battle. Game Boy Advance. Sega. Area/level: Story Mode. "Phi: Located! Located!"
  5. 5.0 5.1 Sonic Team (27 February 2004). Sonic Battle. Game Boy Advance. Sega. Area/level: Story Mode. "Phi: Retreat! Retreat! / Narrator: Phi has run away..."
  6. Sonic Team (27 February 2004). Sonic Battle. Game Boy Advance. Sega. Area/level: Gimme Shelter (Cream's Episode). "Phi #14: Shield to maximum! Let's go, #13! Power to maximum! / Phi #13: All right, #14!"
  7. "Dr. Eggman in... My Greatest Invention". Sonic the Hedgehog: Rival Edition. Tomy. 2017.