In the northeast side of Mothermouth is a tunnel that leads into the Moonstone.
In the New Prophecy game, there is an exit not shown in this picture that lets you begin the Great Journey.
Talking to StarClanEdit
Besides in dreams, going to the Moonstone is the way the Clan cats can talk to StarClan, their ancestors, in the Original Game (in the New Prophecy, there is the Moonpool). In the games, talking to StarClan at the Moonstone is limited to a few events - simply going to the Moonstone is not a guarantee of talking to StarClan.
On the occassion of those few events, the cat who talks to StarClan goes right up to a large glowing rock/gem in the centre of the cave, which is the Moonstone itself.
Party and AlliesEdit
After a certain point in the game, allies will be able to be recruited at the nettle patch, but after they have been recruited, they must be added to your party at the Moonstone.
You must go straight up to the Moonstone and select whether to add or remove (if you already have an ally/allies) allies from their party. Then it shows a list of cats, and whichever you choose will be added (as long as they have already been recuited) or taken away from your party. You cannot be removed from the party in the Original Game.
The first major event to take place at the Moonstone is when the player goes along with Graystripe, Tigerclaw, Bluestar, and Ravenpaw to the Moonstone so that Bluestar can talk with StarClan. Bluestar recieves a message from StarClan stating that the Clan is being attacked.
The next time that the Moonstone is shown in the Original Game is when the player becomes leader of ThunderClan and goes to recieve nine lives and a leader name. The nine lives are from: Lionheart (courage), Redtail (justice), Silverstream (loyalty), Runningwind (tireless energy), Brindleface (protection), Swiftpaw (mentoring), Yellowfang (compassion), Spottedleaf (love), and Bluestar (nobility, certainty, faith). The ceremony is interupted when you see a hill of bones and here the prophecy "Four will become two, and blood will rule the forest" is presented.
The Moonstone is also used in The Depths of Mothermouth.
Deep Mothermouth is accesible after you have completed the subquest, The Depths of Mothermouth. (Original game only) Here, you can