Testing

 I was summoned to yet another parallel universe.

"Who has summoned me?"

A rather weedy young male looked up from behind several crudely made (and woefully incomplete) protection sigils. 

"I did! I demand power!"

I glanced down at the magic circle I was supposedly trapped in.

"You know, of course, that I must give you a weakness in exchange for this power, yes?"

"Yes, of course!" He lied.

"Once you've killed a million creatures, you will die yourself. Agree?"

He nodded, I gave him the power then he died a second later thanks to all the micro-organisms inside him dying.