A locator orb is an item obtained by giving Ava an inert locator orb during Dragon Slayer II. After some adjustments, she will give you a locator orb to track down the Morytania dragon key piece.
Each use of this orb will reduce a player's health by 10 hitpoints down to a minimum of 1 hitpoint and cannot kill the player, similar to a dwarven rock cake. Because of this, it can be beneficial to use in combination with the Dharok's armour set. This method can also be used effectively in Nightmare Zone as it does not affect a player's absorption count.
If lost or manually "destroyed", the player can speak to Ava about "a key" for another one. After completion of Dragon Slayer II, the chat option changes with the player asking directly for more orbs instead.
Like the dwarven rock cake, players may own multiple locator orbs at a time.