Mrs. Lenz

"Do you want a Christmas cookie? You're my cookie, and I could gobble you up!"

- Mrs. Lenz to her (grand)daughter Agnes Mrs. Lenz is the mother of Billy and Agnes Lenz and the tertiary, but true main antagonist in Black Christmas. In additon to being Agnes's mother, she is also her grandmother, due to the fact that Agnes is the biological daughter of Billy. Although she is not directly responsible for the massacre in Black Christmas, her abhorrent parenting and ghastly behavior play a major role in Billy and Agnes's murderous behavior.

Although Billy and Agnes are mass murderers, they are heavily portrayed in a tragic way. They have no understanding of right and wrong. All because of their mother. She is portrayed by actress Karin Konoval.

1974 film
Billy's mother's name is never revealed in the original Black Christmas, nor is she ever shown. The only reference to her is Billy (or possibly Agnes) doing an impression of her over the phone.

2006 remake
In the remake, much more is revealed, although still no name is given. She and her husband deeply despise one another (for unknown reasons). After Billy is born, his father has deep affection for his newborn son. His mother, on the other hand is disgusted with the baby. She even goes so far as to drop broken glass in his crib.

When Billy is five, she tells Billy he isn't going to get anything for Christmas. She lied to him saying the Russians murdered Santa by shooting his sleigh down, much to her husband correcting her. Soon after, her boyfriend shows up, and the two of them murder her husband and bury his corpse underneath the house. She then locks Billy in the attic, giving him no human interaction at all.

Seven years later, Mrs. Lenz is trying to get pregnant, but is having trouble conceiving with her new husband as he is discovered to be impotent. She hears Billy in the attic one night, and decides to go up and rape him. 9 months later, Agnes is born. Agnes is her mother's pride and joy, and is given the life Billy never had.

Eight years later, on Christmas, Agnes is opening gifts from her (grand)mother. Mrs. Lenz, who is starting to grow tired of Agnes as well, goes into the kitchen to answer the phone. Billy is on the other line threating her and Agnes. As she runs back in the living room, Agnes is gone. Her and her husband run up to the attic to try and find Agnes. But then hear screams down stairs. They walk in to find Billy tearing out Agnes's eye and eating it. Billy's stepfather tries to attack him, but Billy impales him on a Christmas ornanment, killing him in one hit.

As she bawls in defeat, Billy strangles her with Christmas tree lights. He drags her body into the kitchen, and violently beats her to death with a rolling pin. He then cuts large chunks out of her back with cookie cutters, which he cooks and eats.

Quotes
""Why do you bother putting up with those cookies? Santa Clause ain't coming to see you.""

- Constance putting down Billy when he is putting up Christmas cookies ""Russians shot down his sleigh. Santa Clause is dead!""

- Constance lying to Billy about Christmas ""He is my boyfriend.""

- Constance introducing her lover to her husband ""Gonna be my husband! He's my family now!"

- Constance announcing that she's going to marry her lover then kills her husband as proof ""Every goddamn time!""

- Constance's frustration when her attempt to get pregnant fails when her husband falls asleep during sex ""My little Agnes!""

- Constance expressing her joy at her daughter/granddaughter's arrival ""She's my family now!""

- Constance to Billy when she hears him from the attic and looks at the ceiling ""Merry Christmas, Agnes!""

- Constance as Agnes opens her Christmas presents ""There's nothing up there!""

- Constance to Agnes when she asked if Santa's reindeer are upstairs as noises came from the attic ""Merry Christmas. Merry Christmas. Hey, Merry Christmas!""

- Constance yelling into the phone when no one answers before being taunted by Billy ""BILLY!! What have you done?!""

- Constance yelling at Billy when she discovers that Agnes is gone ""NO!!""

- Constance's last words as she watches her lover die before she gets strangled and beaten to death by Billy