Saw this somewhere else.
Imagine a man named Bob. He is standing, all alone, on a perfectly flat ground made of nothing in particular. This ground extends infinitely in all directions. Above him is a nothing-in-particular sky.
The first post will be an attempt to kill Bob. You do this by summoning something. Be specific: don't just say "I summon ___.", say "I summon ___ to do ___.", unless it's obvious what you want it to do. If it's obvious, explaining it ruins the fun. (For example, if someone summons Geek Squad, then summoning layoffs would be obvious.)
The next post will try to save Bob by counteracting the first post. You do this by summoning something else, be specific here also. You can give Bob something to use and tell him what to do with it.
The next post will also have the goal of killing Bob--by counteracting the measure previously taken to save him. Then the next post tries to counteract that, then the next post tries to counteract that...
Note that Bob WANTS to live. Killing attempts cannot influence that. No one can directly control him, but people trying to save him can instruct him on how to use something towards his best interests.
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I'll start:
I summon a zombie to eat Bob's brains.
