The 10th squad sigil is an item worn in the amulet slot that allows a player to teleport to the last battle in the Monkey Madnessquest. It has no uses after the quest, as the teleport option no longer functions.
If lost, the sigil can be re-obtained from the gnome Waymottin at the end of the Ape Atoll Dungeon; you can also obtain multiple sigils from Waymottin by using the drop trick or by banking them.
During the quest, Glough casts a spell which summons all members of the 10th squad to the battle site, hoping to get them killed by a jungle demon. By wearing a 10th squad sigil, players were identified as aligned to the squad and thus were able to aid them in defeating the demon.
In an update, all the gnomes in RuneScape were graphically reworked, and the sigils they wore, although the players' sigil didn't receive an update.
If you tried to wear this during the 2009 Easter event, the Easter Bunny advised you to remove "The sigil you're wearing", not wanting to cause any trouble underground.
Shortly after the sigils were released, some people noticed it had almost no restrictions as to where it could be used. Once equipped, one would wait 5 seconds and then be teleported to the boss fight. As this was not an intended feature and was abused by players, Jagex eventually patched it, making it work like a normal teleport, meaning players could not teleport out of locations where teleports were already blocked.
On 21 February2012, the teleportation method on the sigil was changed from equipping to rubbing.