Orcs of the Misty Mountains
Their origin, and when they settled those tunnels is not known. Sauron must have taken at least some control over them when he settled in Mordor. By the end of the Second Age, Orcs of Mordor had come among them, and under their command the Orcs of the Mountains ambushed and killed Isildur at the Battle of the Gladden Fields.
After the fall of Moria in Third Age 1981, Orcs of the Misty Mountains entered and occupied its ruins. Long afterwards, Moria became the seat of an Orc-chieftain named Azog who slew King Thrór of the Longbeards, and so started the War of the Dwarves and Orcs, in which Azog himself was slain.
Around Third Age 2747 the Orcs of the Misty Mountains became more bold, daring to invade Eriador. The Rangers of the North fought many battles trying to hold them back, but one party managed to reach the Shire. They were fought off by a party of brave Hobbits under Bandobras Took, who killed their leader Golfimbul in the Battle of Greenfields.
After that, the Orcs lurked among the Misty Mountains, and in Third Age 2941, a group of them led by the Great Orc, captured Thorin and Company in the High Pass. They escaped, killing the Great Goblin in the process. Soon after, Azog's son, Bolg united the Orcs of the Misty Mountains and led them east to fight the Battle of Five Armies. That battle ended in defeat for the Orcs, and left the Misty Mountains free of them for many years afterwards.
By the time of the War of the Ring, the Orcs of the Mountains reclaimed Moria but fell under the command of Sauron and Saruman. There were Orcs from the Misty Mountains, in the party that captured Merry and Pippin at Parth Galen.
Legend says that the Longbeards eventually succeeded in recapturing Moria, so the power of the Orcs in the Misty Mountains must have waned considerably after the Third Age if they survived at all.