Mothermouth

Mothermouth is a large cave opening, leading to the Moonstone. Though not confirmed, it is believed to be the beginning of the range of mountains. It's beyond Clan territories and is considered a sacred place to the Clans. When a cat goes through the tunnel inside, it leads deep into the earth, to the cavern where the Moonstone lies. Mothermouth, and the Moonstone, was discovered by the first WindClan medicine cat, Mothflight, who was always un-warrior-like with her dreaminess. The Mothermouth was a old mine that was abandoned by Twolegs.

How it Was Discovered
Mothermouth was first discovered by ancient WindClan warrior Mothflight, who was restless, easily distracted and forgetful. One day, when chasing a feather, her curiosity took her too close to the Thunderpath, where she was nearly killed by a monster, if Gorsefur, the WindClan deputy, hadn't rescued her. Wind was upset because they could have both been killed. However, her drawbacks got her exiled from her Clan, and she followed a path to Mothermouth because it was "calling to her." Clueless, she had discovered the Moonstone and became the first medicine cat of WindClan. In a dream given to her by starclan, she was told to return to the Clans, and Wind appeared, somewhat dazed, but agreeing to allow Mothflight back into the Clan. Afterward her return, it is believed she travelled to other Clans and told them her dream. Only much later was the half-moon "code" added in place.

Description
Inside the Mothermouth is a tunnel, leading to the Moonstone. The Mothermouth got its name, because of its very large opening to the Moonstone. Mothermouth also has two tunnels, one to the Moonstone, and the other that goes somewhere deep into the earth. Cats must find their way through a tunnel by using their whiskers to feel the edges of it, ) or by following the scent trail of the cat ahead of them. The tunnels of the Mothermouth are very rocky and may cut the pads of a cat if they have gone down the wrong tunnel. There are tunnels branching off in opposite directions, but only one leads to the cavern. Once they enter Mothermouth, the cat must stay silent, and the other cat does what she/he normally does to the Moonstone. The Mothermouth can be cold when a cat enters.

Purpose
Cats come here as part of various ceremonies, such as medicine cats sharing tongues with StarClan every half-moon, and leaders gaining their nine lives. Leaders and medicine cats also come here if they need guidance from their warrior ancestors, but cannot wait for members of StarClan to walk in their dreams or have not seen them for many moons and need guidance. Mothermouth appears in all leader ceremonies held in the forest. Cats go to Mothermouth to go to the Moonstone.

When leaders go to the Moonstone, they are forbidden to eat or drink anything beforehand, including traveling herbs. It is also a requirement that all apprentices visit Highstones before they can become warriors. There are two known exceptions to this rule. Bluefur was taken to the Mothermouth by Pinestar when she was a warrior because Pinestar had been busy, and neglected to take her to the Moonstone. Bluefur's littermate, Snowfur, also did not make the trip to Highstones as an apprentice, and it is still unknown whether or not she visited the Moonstone at all. Snowfur did not attend the trip to Highstones with Bluestar and Pinestar because he thought that three capable warriors would look like invasion and trespassing to the wary WindClan warriors, but two warriors would seem innocent enough to cross without picking a fight.

The second known exception is Squirrelflight; according to The New Prophecy: Midnight, she had never been to the Moonstone before she and the five other journeying cats left, as confirmed by Brambleclaw when he sees how nervous she is traveling through WindClan territory. When they returned from their journey, in the time between them getting back and the Clans leaving for the Lake she never officially went with her leader, except for when they passed it on the way to the Sun-drown-place, on the way back, and on the way to the Lake.

When the Clans reach their new home,after the events of Midnight, Moonrise, and Dawn, cats believe that the lake is not their home, because they did not find another Moonstone, until Leafpaw had a dream from Spottedleaf who led her to it, which earned her her full medicine cat name, Leafpool.

The tradition in which apprentices would journey to Mothermouth was not used any longer after the Clans moved to the Lake. This tradition was briefly mentioned in Outcast when Squirrelflight says that apprentices don't travel beyond the Clan territories as they did before in the old forest, so the three apprentices, Jaypaw, Hollypaw, and Lionpaw, should be allowed to go to the Tribe of Rushing Water's mountain home.

It is known that Pinestar, Goosefeather, Featherwhisker, Sunstar, Bluestar, Firestar, Cinderpelt, Yellowfang, Littlecloud, Barkface, Mudfur, Mothwing (she only shared tounges with StarClan once), Leafpool, Runningnose, Blackstar, Leopardstar, Firestar, and Nightstar (StarClan did not grant him nine lives) have been to the Moonstone at least once.

In Shattered Peace, Ravenpaw and Barley journey to Highstones because former BloodClan rogues had driven them out of their home. Ravenpaw then dreams of StarClan in Mothermouth. They tell him that ThunderClan will help him and Barley get their home back.

Mothermouth, and the Moonstone, is left behind when the Clans leave the forest in Dawn, and replaced with the Moonpool in the Lake territories, which is discovered by Leafpool when she was an apprentice and previously used by the ancient version of the Tribe of Rushing Water, in which Rock was a leader.

Into the Wild

In Into the Wild, Firepaw, Graypaw, Ravenpaw, Lionblaze, Tigerclaw, and Bluestar go and take Firepaw and Graypaw to the Mothermouth for the very first time. When it's time for Bluestar to go inside of the Mothermouth, she asks Firepaw and Tigerclaw to go in with her. Tigerclaw ends up leaving, because he was afraid of the power of the Moonstone, but Firepaw stays. Bluestar says that Tigerclaw is a strong warrior on the outside, but softhearted on the inside. When they leave, Firepaw asks Graypaw and Ravenpaw what Tigerclaw said when he came out. Graypaw says that he was just checking if they were still guarding the cave. He then adds Ravenpaw is jumpy with Tigerclaw around. The young apprentice says it was creepy near the Mothermouth, and Graypaw half-heartedly agrees.

Fire And Ice

It is mentioned by Nightpelt that he will go to Mothermouth to get his nine lives and receive the name Nightstar, even though he doesn't.