Timetravel

You wake up one ordinary morning to find a device on your nightstand, left by your older self. No explanation, no instructions beyond a few cryptic warnings. The device lets you travel through time — anywhere, any era — but charges are finite and the cost of a careless change is paid by everyone, including you. There is no quest. There is no chosen-one destiny. There is only the device in your hand, the world's entire history in front of you, and the slow accumulation of consequences from every choice you make. What you do with this is yours to decide.