Runes are small, weightless stones that allow players to cast spells using the Magic skill. Runes can be either bought from the various Rune shops, traded with other players, created from rune essence or pure essence through the Runecrafting skill, obtained from drops by killing monsters, or picked up from spawns on the ground.
The elemental runes (air, water, earth and fire, named after the Greek classical elements) can be substituted for by wielding a respective elemental staff, battlestaff or mystic staff. The only times an elemental staff cannot be used to substitute for runes is when setting up a portal in the Portal Chamber of a player-owned house.
Runes come in a number of different types, but they can be categorised according to themes based on their names. For example, mind, body, blood and soul are all constituent parts of a human; cosmic and astral pertain to outer space; nature is in Guthix, law is in Saradomin, and chaos is in Zamorak; and life and death occur in time. The six combinations runes (mud,mist, lava, smoke, steam and dust) cover all possible pairs of the four elemental runes.