Heidi Sharper Image ads too racy for ... Fans and friends attempted to guess Klum's costume throughout the process.
Inside, guests danced along to a set by DJ Questlove - who was dressed as one half of Grant Wood's American Gothic painting - and sipped on Halloween-themed cocktails before cramming into the venue's narrow entryway to get a glimpse of Klum making her entrance.
The process of applying the costume and the makeup took over 12 hours as Klum shared live videos on Instagram and with Amazon Prime Video, which sponsored the bash.
Heidi Klum has finally arrived at her Halloween party and her arrival was definitely worth the wait! On the red carpet, she hissed and clawed at cameras, showing off her costume's organ-like prosthetics, stitching and wires.
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Klum gets ready for her 2019 event.
Yikes. This might be her most intense look yet.
While Heidi may be the reigning Queen of Halloween for the last two decades, she's not the only one getting into the spooky spirit, with celebs like Kim Kardashian, Cardi B and Ariana Grande doing their takes on famous characters from film and TV.
Look, I'm going to be honest: I don't know what the hell this is.
According to the Daily Mail, the celebrity managed to give the attendees "the shock of a lifetime" as she emerged wearing a costume of a "gory humanoid alien" and accompanied by her husband Tom Kaulitz dressed in a bloody space suit.