Mother G

 was a woman present in multiple time periods but was "not really" a time traveller. When she privately told the Thirteenth Doctor what the "G" stood for, the Doctor didn't believe her. (COMIC: Mistress of Chaos)

Biography
She washed laundry at Castle Houska in 1601. She gave Yasmin Khan, Graham O'Brien, and Tycho Brahe directions to Dagmar Ruskovitch's study. (COMIC: Herald of Madness) Yaz remembered this encounter when meeting Mother G on Venus. (COMIC: Mistress of Chaos)

Mother G also took care of the vegetation at the Icarus Incorperated building on Acantha. She was unaffected by the zero-gravity field created by the Thirteenth Doctor. (COMIC: The Power of the Mobox)

On Venus, Mother G was the head cook at Freedom Thoughtcasting Network. (COMIC: Mistress of Chaos)

Skills
Mother G could sense when people were infected with chaos. Her eyes glowed when she made holes appear in building floors.

Mother G knew the the Doctor's TARDIS and the TARDIS recognised her. She said the TARDIS owed her a "favor or two", and thus convinced the TARDIS to enter a pocket of chaos in the rational universe to save the Thirteenth Doctor. (COMIC: Mistress of Chaos)

Appearance
Mother G was a woman with dark skin and wavy, black hair. She wore green robes with yellow squares and black lines. She also wore cold earrings and a gold bracelet. (COMIC: The Power of the Mobox, Mistress of Chaos)