The subject of this article originates from non-canonical sources. To find out about what is considered "canon" see LOTR:Canon.
Guldur Orcs are a group of orcs who settled in the ancient fortress of Dol Guldur in approximately TA 2941, none of them was from the abandoned fortress, but were from Moria which mainly from Mount Gundabad.
When Azog the Defiler paid homage to the Necromancer of Dol Guldur (Sauron) made a pact in which Azog would bring the armies of the Misty Mountains to conquer the North of Middle-earth and to revive the ancient kingdom of Angmar. During the quest to reclaim Erebor from the Dragon Smaug, many of the Orcs of Dol Guldur met in the Sorcery Hill and began to forge weapons and armors to prepare for war in the east region of Rhovanion. After Gandalf was imprisoned by Sauron, all the Dol Guldur Orcs departed for the Lonely Mountain. During the Battle of Five Armies, Azog lead a Legion of Dol Guldur Orcs, fortunately the orcs were defeated and annihilated in this battle, though with leaving the forces of good with terrible losses as well. ( the battle wouldn't have been won if Thorin did not charge and rally his comrades.)
These Orcs were the same size if not even larger than the Uruk-hai - they were almost identical with other Guldur Orcs and they were disciplined when in their formation. They carried unusually small but long strapped shields and also wielded glaives long as pikes and used them with one hand. Their armour was full-plate over their skin, for they did not wear any padding underneath, which may be the reason why they are quite agile while wearing heavy armor. They also wielded war-cleavers, instead of scimitars or swords.
Their officers had horizontal wedges on top of their helmets and carried two polearms, a war billhook and a shortened version of their infantry's glaives.
Some were pale and others were brown, some were black and some were grey, they varied in size but the majority stood as tall as a human.