The orb of protection is a quest item that the player must recover during the Tree Gnome Village Quest. At the start of the quest the orb has been stolen by Khazard troops and this one is currently being held in the Khazard stronghold north east of the Tree Gnome Village.
To recover this orb the player must break a hole in the stronghold's defences using a nearby ballista and then climb in and reclaim the orb.
It used to be that if you searched a chest in West Ardougne after using the ballista to knock down the wall of the Khazard stronghold you would receive the orb of protection, even if the orb had not been retrieved in the conventional way. This was useful to low levelled players who wished to avoid damage taken from the Khazard commanders inside the stronghold. Very few people knew about this glitch however and therefore was rarely used by anyone.