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

"It doesn't look very hot"

The Obelisk of fire is located in Taverley dungeon near the black dragons. It is the only location where the Charge Fire Orb spell can be cast, requiring level 63 Magic. When the spell is cast on the obelisk, it will turn one unpowered orb into a fire orb, giving the player 146 Magic experience. This charged orb can then be added to a battlestaff to make a battlestaff of fire, granting 125 Crafting experience.

Obelisk of fire in Taverley dungeon.

See also