Her grief.

yeah... but the dog really does die, right?

Ha, yeah. After that happened, I thought she was going to do more things that the book had outlined, too. I'm not sure now, but I think the book showed the boy dying, or her killing him, something like that.

The Babadook symbolized grief, loss and depression, and took the form of her dead husband. "You can't get rid of the Babadook" - You must learn to live and cope with your loss. This is why, at the end, the Babadook isn't gone or destroyed; he's being kept at bay in the basement.

I think it's depression because this is what I immediately thought of at the end of the movie:

https://youtu.be/tGymr78FtbU

I think the Babadook is a manifestation of her repressed grief, postpartum depression, and inner struggle in regards to her son. She doesn't handle any of them and the Babadook eventually settles in. "If it's in a word or it's in a look, you can't get rid of the Babadook." She finally is forced to really confront these things through him: interacting with images of her deceased husband as well as re-watching his death, and when she's partially possessed she verbally abuses and tries to physically hurt her son.

"I'll wager with you, I'll make you a bet. The more you deny, the stronger I get. You start to change when I get in, the Babadook growing right under your skin."

Sam, her son, says "I know you don't love me because the Babadook won't let you" and in the basement when he has her trapped he also says "you let it in, now you have to get it out," and she proceeds to struggle and throw up an inky black substance, after which she no longer shows signs of possession. After being forced to relive her husband's death, she pushes back hard against the Babadook and fights him with anger. When I was watching, I was thinking to myself she needs to stop being scared and instead harness the raw power of rage to confront all the injustice. She eventually does! After screaming at him and yelling that he's nothing, he and the dark aura in the room shrink before he drops to the floor. When she tries to lift his hat, he flees to the basement (where she'd been keeping her husband's things) and that's where the Babadook is from then-on kept at bay.

After facing and handling it, it's stored away and kept in check. For the first time, she's able to really bond with her son, understand and enjoy him.

@Phasmophobia said:

The Babadook symbolized grief, loss and depression, and took the form of her dead husband. "You can't get rid of the Babadook" - You must learn to live and cope with your loss. This is why, at the end, the Babadook isn't gone or destroyed; he's being kept at bay in the basement.

Just finished it. Thank you for that explanation. I feel dumb for not fully getting it right away lol.

@HEYitzED said:

@Phasmophobia said:

The Babadook symbolized grief, loss and depression, and took the form of her dead husband. "You can't get rid of the Babadook" - You must learn to live and cope with your loss. This is why, at the end, the Babadook isn't gone or destroyed; he's being kept at bay in the basement.

Just finished it. Thank you for that explanation. I feel dumb for not fully getting it right away lol.

You're welcome!

Where he needs to be fed and chained up. Surely he was real on some level

Indeed, the story is a metaphor. In the movie the monster does exist, the dog dies and the monster is kept on the basement.

But the story represents the bad feelings she started developing after her husband death and son birth. Instead of treating them she kept denying she needed help, and things got bad to point that friends and family got away from them.

It started affecting her son behavior then she herself was affected. She needed the help and support of her son to fight and release it. But it doesn't die, the basement represents all bad memories she has and where she keep them. She didn't wanna go there, but now her son gives her strength to fight those bad feelings. She often goes down there, when she feels it all again hit her, but she resists these feelings and calm them down.