Anna Strong

Anna Strong is the secondary antagonist of the X-Files episode, Familiar, she is the one responsible for summoning Mister Chuckle Teeth to the town and thus shares accountability for all the murders he committed, even if she ultimately gave her life to stop him.

Biography
Anna Strong was the wife of Chief Strong and became embittered after he had an affair with another woman named Diana, unknown to any of the townsfolk was that Anna was a witch who still followed the black magic of the Salem witchcraft era - she decided to use this magic to place a curse on Diana as vengeance but in the process she unleashed a demon of considerable malice and intelligence, which she could not control.

The demon thus went on a brutal rampage, killing Diana's young son and then Anna's own daughter before inciting chaos and ruin in the town which resulted in Chief Strong lynching a man suspected of killing the children - only for Strong himself to get attacked by Chuckle Teeth in his home, who magically caused Strong to kill Rick, the husband of Diana.

Finally Chuckle Teeth murdered Diana in the forest and Chief Strong came across Anna in a circle, desperately trying to reverse the curse, realizing his wife was the one behind the horrors of the last few days Chief Strong could do little before he became Chuckle Teeth's next victim and was killed.

Mulder and Scully arrived in time to see Anna struggling with flames and trying to banish Chuckle Teeth, despite the agents attempts to stop her it was too late and she soon burst into flames, dying but apparently dispersing Chuckle Teeth from the town in the process.

Abilities
Anna Strong is a witch of significant power but she was not nearly malicious nor strong enough to control the demonic powers she summoned - while it is unknown the exact branch of magic Anna practiced it was likely a form of theistic Satanism (or demonaltry) - considering her revulsion at the evil deeds of Mister Chuckle Teeth however Anna likely didn't truly worship evil and used magic as a form of vengeance : this would make her more akin to a chaos-magician, who does not follow a particular creed but instead does whatever magic they feel gains them results.

Trivia

 * Mulder makes note of historical cases of witches suddenly setting themselves ablaze in the past, suggesting that other witches before Anna had the misfortune of summoning Mister Chuckle Teeth and had to resort to a similar ends to defeat him.