Eternal Fire is one of the most sought-after crafting materials in Wrath of the Lich King. It can be acquired by combining 10 Crystallized Fire, which drops in amounts of 1-2 from Fire Elementals around Northrend.
Farming Primal Fire in TBC Classic
Primal Fire is created by combining 10 Motes of Fire. These Motes drop from any Fire Elemental in the Outlands and can be sold individually as well. There are three major locations where Primal Fire can be farmed, which I will go over here.