To craft runes players need blank rune stones called essence. There are two types of essence: Rune essence and Pure Essence, both are unstackable. They are most commonly referred to simply as 'Ess.' Several other common slang names include 'Pures,' 'P ess', 'Pure ess,' and 'Rune ess.'
Rune essence is dramatically limited in its potential on members servers. It is only capable of being bound at altars available to non-members - into Air, Mind, Water, Earth, Fire, or Body runes. You will be unable to craft member's runes such as Chaos or Nature. This form of Rune Essence is often called "normal essence" or "regular essence" to distinguish it from Pure essence. It requires only level one in mining to mine, but Rune Mysteries must be finished before you can access the mines of Rune Essence.
Pure essence can be used in the creation of any and all runes. This really nice kind of essence is the only kind of essence that can be used to craft Cosmic, Chaos, Astral, Nature, Law, Death, Blood, and the various combination runes such as Steam, Mud, Lava, etc. Runes crafted at the Ourania Runecrafting altar must also be made with pure essence. In order to mine any amount of Pure Essence,and several millione a player must be a Member with at least level 30 Mining and have access to the Essence Mines.
There are multiple ways to obtain rune essence or pure essence. These include trading with other players and purchasing from the Grand Exchange, mining it, monster drops, rewards from the The Great Orb Project, and the daily reward from the Ardougne Tasks or wicked hood.