Demon X Human plot:
[b]Hero Summoning Gone wrong[/b]
Your Character: is an heir to the throne of your kingdom of whatever race you feel like. In a war between another race (Even Demons) your race is losing ground and the enemy is advancing on you by taking your fortresses and cities. It doesn't look good for you, so in a moment of desperation, you seek to summon a 'Hero' from another world to aid you. 

You perform the summoning ritual and Bam someone suddenly appears. However, the one who does appear is far from a refined hero.

My character: Is a Demonic Prince who have been banished to the 'Void' between worlds after a fight with his siblings. My character is an Incubus and part sloth demon who hardly lift a finger for anything that doesn't motivate him. However, he's very powerful, and could easily turn the war in your favor or get back on his siblings if he had the motivation. 

Anyone could be Dom or double switch in this really.