The Northern Waste was a cold and icy region in the far north end ofMiddle-earth, including the realms of Forochel and Forodwath, located above Mount Gundabad and the Ered Mithrin. It was composed mostly of snow and ice; however it did have several great frozen lakes. Little is known about the area.
The Cold-drakes, which plagued the Dwarves often, came from these realms. It is likely that the "Goblins and Hobgoblins" that later colonized the Ered Mithrin drove most of the Cold Drakes back into the Northern Waste.
There were also men up in the wastes called the Lossoth. They lived in different tribes and were often at war with eachother, especially against the tribes in Forochel and Forodwaith. It is also said that some of the Northern Waste Tribes aided the Witch King during his destruction of Eriador. It was most likely because of their disliking of the the southern regions and out of fear. The less hostile Lossoth of Forodwaith and Forochel stayed neutral until the last king of Arnor (King Arvedui) came out of hiding in Mt.Gundabad and asked for aid from the Lossoth of Forochel. They unwillingly aided him. He later took a ship through the Icebay of Forochel, but perished in a storm and sank to the bottom of the sea along with the palantir of the North.
It is also possible that this is where the Snow Trolls dwell. Snow Trolls never appeared in Tolkien's work but it is infered that they exist because there is an encription of one on the Horn of Helms Deep