I'm currently running a SM campaign featuring the orc horde as well. Some things to remember:
- Quantity has a quality all of it's own. Give the horde ridiculously high numbers: 20 - 30 times the size of the whole silver marches armies combined. Add in tribes of giants, trolls, bugbears, goblins. Throw in a couple of white dragons. Now you have a horde.
- Use FR specific stuff:
1) Orogs: are basiccally LE military orcish leaders. Think Hobgoblins on steroids. They've become the warrior elite of Obould's army, giving him a core "legion" of disciplined fighters, besides the power of his shock troopers.
2) Fiendish Orcs: Forgot there name, but they were bred in Ascalhorn (Hellgate Keep) and they're orcs, so they multiply at outstanding rates.
3) Fey'ri: The levish half fiends are roaming free, and probably wouldn't be adverse to an orc horde helping them cleanse the land....
4) Duergar: They want Mithril Hall back.
5) Drow: They want Mithril Hall Gone!!
IMC, i have had the PCs run into all these groups in some way or another. basically, everybody is being manipulated by an ancient Lich descendant of the Netherese, who is searching for the last Nether Scrolls. The BBEG wants chaos unleashed in the SM so that he can do his "Dastardly Plan" without the pesky interference of the leaders of the SMs.
Anyhow, my campign is based more on the Uthgardt Tribes: I'm going for a "Barbarians save Civilization" theme this time.
Hope this helped.
NOTE: Orc heroes Rock!! A Barbarian/Ranger Orc Scout can get a move of 60' and very high hide bonuses. Now that is a good skirmisher. Orog cleric/fighters are also good. Eyes of Gruumsh have a lot of flavor. And I can't stress this enough: as an orc Horde leader, always hire Kobold sorcerors to cover your back....
