Here is an inspiring post about remixing your standard orc.
To sum up, an orc tribe that was on the rocks prayed to their gods. In return they received the Sanguine Grail: an artifact that allows the orcs to, painfully, extract powers and knowledge from their victims. This means your average hulking brute orc is now smarter than every one of your PCs, save for the wizard. To boot, they also have advantage on fear effects and can communicate telepathically. Occasionally an orc will also be able to cast a 3rd level spell.
This means the tribe's warriors are organized, disciplined, and no longer tied to a strong leader. Any army used to fighting "normal" orcs would be butchered by these creatures. They will also have a fondness for taking prisoners, especially wizards...
As long as the Sanguine Grail exists, the threat of these creatures will remain, much to the chagrin of whomever you need to foil.
I tossed together some 5e stat blocks. Who knows, maybe I'll use them in the new campaign.
Enjoy. Let me know what you think.
Update: My second blog on this concept, discussing military and technological change, here.