The Beast
Something has crash landed on your outermost mining outpost.
It's on the belts now.
Your inserters have stopped doing what you told them to.
It arrives 20 minutes into a new game, or 20 minutes after you add the mod to a save. If you can't wait, /beast-arrive will bring it to you now.
There's nothing to research and nothing new to build. You have what you have.
Needs only the base game. Space Age works too.