The Hero We Need

You've been putting the finishing touches on your time machine for years, and now seems like the perfect time to put it to the test. After 9 long, hard years tinkering with it to achieve your dream of travelling through time, you think now is the time to find out if this thing can actually save the world.

You had not yet realised that your time machine had no uranium or plutonium, vital to the machine inside it. Without it, you do not know what will happen. It would compact the matter on the time machine and the time machine itself, creating a black hole smaller than an atom, but atoms are the most basic form of matter so something impossible, will become possible... but also mostly like crushing you inside of it into non-existence.

Which element will you try to get hold of first?