Summoner Pathfinder Help

[RBVakarian]

I'm building a Drow Summoner for our next campaign (we start at level 5). I'm wanting to have my character making deals with demons; and my eidolon as a demon of sorts. My GM has ok'd this as long as I have a good backstory, but I'm not for sure why a demon (my eidolon) would pair up with a mortal so closely. Any ideas?

[Thatwarforged]

Corruption, exploring the material plane, sowing chaos and destruction and FOR YOUR IMMORTAL SOUL.

[mythmonster2]

Well, the obvious one is that it wants to tempt you to evil and sees earning your trust as a good way to get started on that. Alternatively, maybe the demon got sent to the Material Plane as punishment and has to earn its way back in, through some means or other that you could work out with the DM. If you want to go a different route, you could have the summoner bind the demon through a ritual, leaving it only helping you because it's forced to at first, and either keeping that up or having it genuinely get used to your presence.

[RBVakarian]

Hmm; maybe binding it specifically to me. A la Howl and Calcifar from Howls Moving Castle? If the demon hurts me, he hurts himself.