Snowfall Frost

Snowfall Frost is a female-unicorn that appeared in "A Hearth's Warming Tail", portrayed by Kelly Sheridan and Starlight Glimmer. She is the antagonist of the story, trying to make Hearth's Warming disappear by casting a spell in a brew, similar to those of a witch.

Appearance
It isn't revealed how the actual "Snowfall Frost" in the story looks like. However, she is portrayed by Starlight Glimmer when she lived in Our Town. Thus, she looks exactly like Starlight Glimmer.

Personality
When she was a filly, she loved Hearth's Warming. But when her teacher, Professor Flintheart, yells at her for liking the holiday, her heart turned cold. Ever since, she hated the holiday and wanted to destroy it.

Professor Flintheart
He is Snowfall's teacher. He didn't like the idea of her liking the holiday.

Rainbow Dash/Snowdash
"He" is her worker.

Ghosts
They each showed her the past, present, and future.

Trivia

 * Many fans complained there to be another favorite Scrooge-inspired story, but with Discord playing the part.