The main RuneScape Wiki has an article on: Obelisk of air
The Old School RuneScape Wiki also has an article on Obelisk of air.

"A tall stone pointy thing"

The Obelisk of air is a piece of scenery located on a mountain in the level 6 wilderness. It can be reached by climbing the ladder north of the Black demons in the Edgeville Dungeon. It is the only location where the charge air orb spell can be cast ,which requires level 66 magic to use. When the spell is cast on the obelisk, it will turn one unpowered orb into an air orb, giving the player 152 magic experience. This charged orb can then be added to a battlestaff to make a battlestaff of air, granting 137.5 crafting experience.

Player has entered obelisk of air from Edgeville dungeon.

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