Am I The Asshole for Leaving my Sister to Die?

I'll preface this by saying that I really don't think I'm The Asshole here, but my whole family has decided otherwise. It's nothing new for them, since they always take my sister's side on EVERYTHING.

So, I've been seeing this guy lately. He's so hot, first of all, that maybe I've got a bit of a blind spot whenever he does something wrong. But that's besides the point. We've been together for months. We're obviously going to get married even though he hasn't popped the question yet and low key I just can't wait to have his babies (don't say anything I haven't told him this yet/don't even know if he wants kids.)

Anyways we were all hanging out together in our apartment. My sister Clara (24F) and I (26F) live together right now, and Damien (6.8BD) were having a few drinks when Damien suggested we play a little drinking game.

Of course, Clara was a buzz-kill like always and said she had to work in the morning. This would have utterly ruined the night. So, Damien talked to her in that soft, low, hypnotic voice of his and she changed her mind pretty quickly.

Damien pulled this old contraption out of the closet that was hidden behind a little hidden panel (he's so secretive, always hiding stuff, even in my apartment!) Next he unwraps it from this oily cloth and hands me the thing it was wrapped up in and I hear like, all these voices in my head, screaming, like they're in some kinda horrible agony or something.

Anyways I threw the rag on the floor because I didn't like hearing the screaming voices in my head and Damien got a little bit mad. Not really mad like sometimes but just a little bit and he yelled at me to pick it up and fold it properly and who raised me and didn't they ever teach me to be respectful of other people's property?

So I picked it back up and tried to ignore all the screaming but sometimes I hear it still when it's really quiet.

After folding it I saw Damien was smiling. I looked at the clock and saw it was a lot later, like 3AM now.

Damien said he'd gotten the game all set up and asked if I wanted to come see it so I went out to the living room and looked.

My sister was all wrapped up in this weird machine, elongated and stretched. Her eyes were blinking on one end and her mouth was on the other side screaming. And then I heard the drip, drip, drip of blood and saw it falling into this little metal box with weird symbols all over it.

Something started to crawl out of the box, and I couldn't help it anymore, I screamed and ran out.

My family was pissed when I told them what happened, they won't even talk to me anymore.

So, Reddit, Am I The Asshole?