Miss Chief was a being in the form of a plump bespectacled woman, who could travel back and forward in time, and used this ability to make trouble for others. She dressed in the attire of a medieval court jester, and had a jester's stick she called Mini-Mischief, which was necessary for Miss Chief to time travel, and it didn't like getting wet.
She brought Matthew Hopkins to the "Witch Hunt" happening during the Coal Hill Halloween Fayre. Clara Oswald, who was dressed as a witch, was captured by Hopkins and after that, Miss Chief sent them back to the 17th century where Clara was put under trial for witchcraft. Clara was thrown into a lake with her hands and legs tied. If she survived, she would be considered a witch. If she drowned, she would be considered innocent.
After the Twelfth Doctor demanded Miss Chief to bring Clara back, she time travelled back to the 17th century, leaving a knife and a small oxygen tank for Clara so she could escape drowning. However, the Doctor was still unsatisfied, demanding Miss Chief to tell him where and when Clara was. Miss Chief proposed a "Time-Space Scavenger Hunt", saying that if the Doctor won the game, she would give him the information he wanted. When Miss Chief brought back ivory from Indonesia, the Doctor claimed she lost the game, because, by the time she collected the item, the place's name was actually "Dutch East Indies". The Doctor went then to rescue Clara, being also held on the 17th century. The Doctor was accused of being a witch and nearly hanged along with Clara, although Miss Chief brought them back to the 21st century. Convincing Miss Chief that he had some mischief planned, she returned them to the 17th century so they could get the TARDIS back and stop the execution of Agnes Leech, who was falsely accused of witchcraft. Clara did this by convincing the mob that Hopkins was a witch and Smudge was his familiar, but the Doctor prevented them from murdering Hopkins by sneakily putting Mini-Mischief in his belt, forcing Miss Chief to save his life. The Doctor and Clara escaped; the Doctor thought that Miss Chief might go looking for them, but doubted she would find them. (COMIC: Witch Hunt)