When you’re living in a universe where your alien forefathers were less than cautious, there’s a serious risk you have to consider when dealing with the artifacts they’ve left behind–and that’s the possibility of an unexpected superweapon. After all, their weapons don’t have to look anything like what our weapons do, and it’s not like they’ve kept the instruction manual lying around, either. You might think you’d be safe, since these ancient weapons haven’t been used in thousands of years, but early alien predecessors had a tendency to build things to last, and hooked in to natural power sources that just don’t quit. Here’s a few of the oldest and most dangerous artifacts discovered… so far.

4. The Planet Killer — Star Trek TOS

While it’s not the most impressive sight to behold when it’s inactive, one glimpse of the Planet Killer in action will change that opinion in a hurry. Built by an unknown civilization and possibly from another galaxy, the Planet Killer does exactly what it says it will: approaches a world, begins to break it down, and consumes the raw material to keep it going. Of course, it’s not limited to planets, as the unfortunate Commodore Decker learned, and starships take only a fraction of the time to destroy. The Planet Killer is made from neutronium and fires antiproton beams, indicating that whoever built it had a pretty sophisticated level of tech, and if it really did cross over from another galaxy, it’d have to be tens of thousands, if not hundreds of thousands, of years old.

3. The Great Machine — Babylon 5

Built deep into the planet Epsilon III, which Babylon 5 was in orbit over, was the device known simply as the Great Machine. Unlike the Planet Killer, the Great Machine wasn’t strictly built as a weapon, providing a powerful platform for communications and sensors, but its destructive capacity still dwarfed that of almost everything deployed by the younger races of the galaxy. The Great Machine requires a sentient being to be incorporated into it for full access, so it’s not quite as likely to be activated by accident as some of the other entries on this list, but the consequences could still be high. Creating temporal rifts and firing massive particle beams, you definitely wouldn’t want to be on the wrong side of this one.

The size of the Great Machine also can’t be understated–even just one of its (many) fusion reactors is miles across, and it stretches thousands of feet under the surface. Even its caretaker didn’t know who had built it or how long ago it was built, but it had been at least 500 years since he took control of it.

2. Dakara Superweapon — Stargate SG-1

The Ancients of the Stargate universe are kind of the notorious case example for leaving dangerous artifacts just lying around, from machines that cause all ships entering hyperspace to just explode without warning to a device that emits radiation which creates exploding tumors. There’s only one thing that can truly be considered the most dangerous, however, and that’s the Dakara Superweapon. Even calling it a weapon is a little reductive; it simply doesn’t capture the magnitude of destruction at work. Built into a mountain on what became the sacred planet of the Jaffa, the Dakara Superweapon can wipe out an entire species across the whole galaxy simultaneously. Yep, you read that right–this machine’s sole purpose is to commit genocide at a galactic level. What could possibly have prompted the Ancients to build this?  They seemed to just like to make these things because they could. Operated by a fairly simple control panel that has to be calibrated with incredible precision, it would be easy to activate by accident, and there’s no way to be sure it’s only acting on one species. The bad guys were seeking it out to destroy ALL life, after all. You’d think it would at least have a confirmation prompt…

1. The Moment — Doctor Who

As with most horrible things the Time Lords created, Rassilon had a pretty big hand in the Moment’s existence. Due to Timey-Wimey, it was never actually used, so it’s hard to say exactly what it was capable of, but the Doctor intended to use it to end the Time War between Gallifrey and the Daleks, so it must have been insanely powerful. At the very least, it initiated the time lock on the War, effectively removing both Daleks and Time Lords from the universe for a period of time. Without even being used, it was still capable of pulling people and objects into each other’s time frames, and seemed to be aware of a number of possible futures which had not yet come to pass. The Moment was also known to be a sentient lifeform of its own, and the main thing which prevented the Time Lords from using it themselves was their fear of its judgment. And even by the standards of the Time Lords, the Moment was extremely ancient.

That’s it for this week. Any other insanely dangerous artifacts that the older civilizations left behind? You can mention them in the comments below!