Pinch
So an unbeliever that managed to summon a Demon by a fluke, things she has the right to command him.
How adorable
But you're in luck milady.
For choosing a Demon from the Fluffy department.
Was it any other,
you would have been killed on the spot...
or worse.
But as you seem to be a clean slate we can make a posthumous contract.
After all, you are just an insignificant insect in the greater scheme of things
So...
"Can I interest you in our lord and savior, Lord Lush the God of Strife and Friendship?"