No, that's not an alien that's sweeping through the void to end your life and consciousness with a single, silent whip of its stringy tentacles. It's a squid.
Which is maybe more terrifying, because it's real.
Magnapinna squids are one of the deep-sea more ethereal creatures. Little is known of these squid as very few have ever been captured … They are unusual in both that the fins are up to 90% of the length of the body, i.e. the mantle, and the ridiculously long length of the arms. The squid often will hold some of the arms at a 90˚ angles from the side of the body.