It depends on which kind of Orc the OP had in mind, the way I see it there are three main interpretations (or rather three interpretations from popular franchises): the evil murderous horde from Lord of the Rings, the shamanistic and honor bound green skins from Warcraft, and the near insane blokes from Warhammer (I know the least about these as I have only read the wikipedia article on them once).
If you want the Tolkien orcs I would use Ghouls as a starting point. But maybe make them a bit weaker and just have them appear in greater numbers with a different catch.
If you have more of the Warcraft orcs in mind than I'd give them maybe a variation of Seelie magic and make them strong, tough, but not crazed bloodthirsty savages. They would have their own social structure and style of government and be fairly independent as a faction.
Yet another option is to make up what you want orcs to be. Whatever best fits the feel of your campaign. However I would steer clear of making them associated with the fae in any regards (unless you have a different interpretation than mine). In my mind most of them wouldn't scheme and think of twenty different ways to screw you over, they would be more straightforward than that. Heck, you could even just borrow Blizzard's plot for them and have the orcs be a displaced race searching for a home, and just tough luck to anyone foolish enough to get into their way.