That's right, like a TSA agent who's discovered an exotic frog in someone's suitcase, you're looking to keep alien fauna and flora from invading the planet.
Thankfully, there's only one location you need to visit to knock this challenge out, and you'll be able to destroy all five alien trees needed to complete it.
Here's where to destroy alien trees in Fortnite.
Alien tree locations
Dead center of the map, you'll find the "Aftermath" location, ground zero of the alien invasion, and the permanently scarred landscape surrounding it. You'll recognize it from all the purple grass and strange alien trees dotting the area.
Here's what a group of alien trees looks like if you need a reminder.
Simply look around for five alien trees (their size doesn't appear to matter for this challenge) and smash them with your harvesting tool or a weapon. You might have to do a little walking, as the alien trees tend to bunch up in groups of three at most, but you can easily finish this challenge in under a minute.
For your trouble, you get 30,000 XP to help boost your season 7 battle pass.
Don't forget to check out our Fortnite guides page for more walkthroughs on this week's legendary challenges, and be sure to grab the latest alien artifacts to further customize your Kymera. Here's this week's legendary challenges, too.