https://www.gamespot.com/articles/fortnites-cube-melted-and-everyone-on-twitter-is-f/1100-6461894/

The mysterious purple cube in Fortnite has finally stopped moving. It ended up falling into Loot Lake and melting. No one really knows why or what any of it means. But hey, Season 6 is right around the corner and will hopefully provide some answers.

It's anyone's guess as to what's actually happening in Fortnite: Battle Royale in the meantime. Weeks ago, a giant purple rift in the sky started shooting out lightning and destroying objects. The final strike left behind a massive purple cube in the middle of the desert. Covered in strange glowing symbols, the cube reacted differently depending on how players interacted with it.