Glass avatar

The Enchanted Glass people, or simply Glass people (TV: Twice Upon a Time), are translucent humanoids made out of glass.

History
Helen Clay started up the Testimony Foundation, a foundation of taking people from their last moments and making them into glass bodies, in 500000012 on New Earth (TV: Twice Upon a Time).

When one glass person tried to take Captain Lethbridge Stewert, there was a timeline error during the process, putting the Captain into the wrong decade. The glass people then took the The TARDIS, with the Captain and the two Doctors inside. While investigating the Ship, the First and Twelfth Doctors find the glass woman, who shows that they have "found" Bill Potts, as a glass person.