I can't tell you what
all of the lore is ... but I can tell you that the Kingdom of Many-Arrows is in the process of being rebuilt.
Self-crowned King Orrusk Homebringer is working to restore an orc domain in the far north, beginning with the shattered fortress of Dark Arrow Keep. The Kingdom of Many-Arrows united the disparate orc tribes of the Spine of the World for over a hundred years until it was razed in the War of the Silver Marches. Orrusk would see it come into being again, and more orcs arrive every day, drawn by his vision of a new, independent orc realm.
EDIT: Did a keyword search for "orcs" in the "A Guide to the Realms" chapter of
Heroes of Faerûn and came up with a few more notable references:
Thar. Valiant orcs fight to defend their territory from ogres, manticores, and perytons in the rocky moorland known as the Thar. Eons ago, this land was a unified orc kingdom. Legend has it that Vorbyx’s Hammer, a great weapon carried by the first king of Thar, lies hidden somewhere here. Thar’s orcs believe that the next orc to wield it will restore the kingdom to its former glory.
Rise and Fall of Muranndin. In the late fourteenth century, an oni couple conquered the city of Murann in southwest Amn and founded Muranndin, a short-lived empire of marauding orcs and ogres who sought living sacrifices for their gods Gruumsh and Vaprak.
Sundabar. Like its sibling-city, Mirabar, Sundabar was both an underground dwarfhold and a thriving surface city until it was razed by Many-Arrows orcs in the War of the Silver Marches ...
vermoors. An unsettled region of fog-shrouded hills, cold bogs, rocky ridges, small peaks, and crumbling ruins, this vast waste is inhabited by hill giants, ettins, ogres, countless trolls, and warring bands of orcs ...
Airspur. The city of Airspur drifts above the shores of Wizards’ Reach on an island of floating stone. Its populace includes a higher-than-average percentage of orcs and genasi
High Moor. Trolls and cruel goblinoids prowl the rocky wilderness of the High Moor, as do nomadic orcs and human berserkers.
