Unlike most villians in FOP, Ms. Doombringer is the first villain to be really taken seriously.
Ms. Doombringer can be considered the equivalent of Dark Danny from Danny Phantom.
Ms. Doombringer is the second fairy hunter to appear in the series, the first was Denzel Crocker.
Like with the Lich from Adventure Time, anytime Doombringer appears, things get serious.
She is similar to Mr. Crocker, with the exception of more weapons and more "craziness".
Ms. Doombringer used to date Mark Brown before he was killed off.
It is implied that Doombringer didn't like Mark Brown, and his spying skills were lousy, as she hired him as a spy to reveal fairy godparents.
Ms. Doombringer killed Jorgen Von Strangle's niece Ginny without his knowledge sometime before Chloe moved to Dimmsdale. She has also killed Jorgen's brother and Ginny's father Trevor, whom Ginny tried to avenge before dying at the hands of Doombringer.