E-107 Theta was an E-100 Series robot that, in an possible future version of Mobius, was sealed inside the Catacombs of Castle Mobius along with former king Shadow the Hedgehog, Tikhaos and the Anarchy Beryl Bomb. Little is known about Theta except that it must have been extremely dangerous as only the greatest threats to Mobius that had to be quarantined were kept in the Catacombs. (SU: #7)
- Why E-107 was quarantined and not simply destroyed remains a mystery.
- The original E-107 Theta from Mobius Prime was the only E-series robot not destroyed by Gamma, as it escaped into the radioactive sewers of Robotropolis. This is likely the reason it had to be quarantined in the future.