Look at the picture in the OP and tell me he can reach his arms that far.
pick up the handle
pick up the black handle.
pick up the black thingy.
stop assuming it's a magnifying glass and notice that it's a sword. With one fluid motion, take it out and swing it at the demon, chopping its head off
Get up and walk a centimetre before falling on your fat ass.
Notice it's the ghost of the guy who made the letter. Apologize.
Clearly, it can only die through means of magic or wizardry. There's no way you can murder it, so you should befriend it.