Twelfth Doctor (Shadow World)

The Twelfth Doctor existed as a virtual construct in one world created by the Monks, so that they could plan the perfect invasion of Earth.

The Doctor shared the history and personality of his non-virtual counterpart, only parting with that history shortly after the events aboard Chasm Forge, meaning that he too was blind. He was a perfect duplicate and, like the rest of the people living within the Shadow World, he believed himself to be real.

History
He was in his lecture hall at St Luke's University when the Pope arrived. After some initial confusion caused by his partial blindness, even with the assistance of his sonic sunglasses, Nardole helped him understand the Pope wanted him to investigate the Veritas, a document that caused anyone who read it to kill themselves.

Travelling to Bill's house, the Doctor interrupted her date and brought her along, hiding the fact he was blind despite Nardole's concerns. When the arrived at the Haereticum, where the Veritas was kept, they found a priest had shot the lockout and read the text. The Doctor instructed Bill and Nardole to go find the priest, and used the time alone to borrow regeneration energy from his future with a device he had attached to his temples, briefly restoring his eyesight. However, before he could read the text, he was confronted by the Monks, forcing him to flee with a laptop instead.

Despite nearly being captured, he made it to the Oval Office, finding the President dead. He listened to the Veritas via the laptop and realised that he was part of a simulation created by aliens that wished to invade Earth. Bill arrived, but was deleted by the Monks shortly after the Doctor told her the truth. Before being deleted himself, the Doctor used the sonic sunglasses to send an email to his real world counterpart to warn him of the impending invasion, musing that he was doing what everyone did when the world was in danger: calling the Doctor. (TV: Extremis)

Other Shadow Worlds
In at least one other Shadow World the Doctor was not successful in contacting his real world counterpart and was killed by the Monks. (TV: Extremis)

Duodécimo Doctor (Mundo Sombra)