The Fourth Age
The Red Book of Westmarch recounts the destruction of Durin’s Bane at the hands of Gandalf during the War of the Ring. This led Dwalin, son of Dori and Éowyn Fairbairn to the possibility that the mines might be abandoned. The orcs may well have been called forth to join Sauron’s army in the fighting thereafter, and even if not, could the orcs really persist in such numbers after a century of peace? This encouraged the Undertowers Adventuring Company to undertake an expedition to Moria to retrieve its lost treasures.
Upon reaching Lothlórien, however, Tauriel informed them that there were indeed orcs still living in the mines. Dwalin wished to at least see the Dimrill Gate after his long journey, and Tauriel acquiesced to grant that request. Marroc Fairbairn, however, managed to elude the elves. Éowyn knew that her brother would find a way into Moria. Once taken to the Dimrill Gate, she recognized that if she did not act then, she would not be able to enter the mines again, and they would have to abandon their quest — and likely her brother. So, she ran into the mines, forcing her companions to react quickly and follow her in.
The orcs are led by a fearsome warchief named Ghazûl.