Place of No Stars

The Place of No Stars (informally known as the Dark Forest) is the opposite of StarClan's hunting grounds: it is a place where cats that have committed great crimes against their Clans and against the warrior code go when they die. However, cats who commit crimes but believe they are following the Warrior Code by doing them can usually join the ranks of StarClan instead (like Mudclaw).

Description
It is described as a vast and empty place; a shadowy forest with no moon or stars visible — the complete opposite of StarClan's hunting grounds, which are warm and sunny. The ground is bare and the landscape is lit only by sickly glowing fungus on the trees. There is no prey and cats feel no hunger. Instead of walking the skies with friends and family, cats here are banished to walk through the forest in solitude, though Tigerstar seems to have found a way to overcome this.

Much like in StarClan, cats of the Place of No Stars who are forgotten by all living cats fade away to little more than ghostlike spirits, who haunt the Dark Forest.

Several cats (most notably Tigerstar) can walk the dreams of living cats. Usually in the dream, the cat finds his or herself in the Dark Forest, with the deceased cat(s) (Although this is not always the case, as with Hawkfrost visiting Ivypaw in a field she dreamed of). There seem to be no limitations on who the Dark Forest cats can visit, although if a cat consciously decides that they don't want to be visited any more, this seems to prevent it from happening again. Upon waking up from the dream, they will retain all characteristics acquired (for example, if they get wounded in the Dark Forest, they will have the same wound in reality as well. This also applies to fatigue, and skills practiced in the dream).

StarClan cats are able to pass into the Place of No Stars if they need to, but by doing so, they risk the chance of becoming lost and never finding their way out again. From StarClan, there is a barrier of sorts consisting of a great cloud of mist, that eventually leads to the Dark Forest. Living cats are able to visit the Dark Forest when guided by a StarClan cat, although on one occasion Leafpool was able to see it without any StarClan cat with her.

Starlight'

 * The Place of No Stars is first seen when Tigerstar visits his sons Hawkfrost in Brambleclaw in their dreams and coaches them in battle skills, and also instills ambition into them. He tells them that they deserve to lead their Clans, or even the whole forest, and gives them tips on how to rise through the ranks of their Clans.

Twilight

 * Tigerstar continues training his two sons, and advises them to work hard in their Clans to try and earn the position of deputy.
 * At one point, Leafpool sees one of their training sessions in a dream, and wonders if she should tell Squirrelflight that her mate is meeting with Tigerstar, but decides against it.

Sunset

 * In the Prologue, Darkstripe and Tigerstar meet each other, and Darkstripe is very confused and scared about the Dark Forest. Tigerstar tells him that they are unable to stay together, as that is part of their punishment, and leaves Darkstripe.
 * Tigerstar still visits Hawkfrost and Brambleclaw, and tries to get Tawnypelt to join him, too, however, she turns him down, saying that she doesn't want to become leader unless StarClan wishes it. Tigerstar and Hawkfrost begin to notice Brambleclaw's reluctance to hurt any cat to become leader, so Hawkfrost tried to set up Brambleclaw to kill Firestar, by trapping the leader in a fox trap, but Brambleclaw refused and fought Hawkfrost to protect his leader. Brambleclaw managed to kill Hawkfrost, who joined his father in the Dark Forest. Brambleclaw never visited the Place of No Stars in his dreams again.

The Sight

 * Tigerstar and Hawkfrost visit Jaypaw in a dream, and offer to train him to be a great warrior despite his blindness, but Spottedleaf appears and takes him away from them.

Dark River

 * Tigerstar and Hawkfrost approach Lionpaw, offering to train him. He eagerly accepts, as he enjoys being a warrior. However, his nighttime meetings with Heatherpaw in the tunnels interfere with his training, and Tigerstar tells him he must stop meeting with her if he wishes to be a great warrior. He reluctantly stops meeting with Heatherpaw and focuses on his training.

Outcast

 * Tigerstar and Hawkfrost continue training Lionpaw, but they are unable to visit him while he is with the Tribe of Rushing Water. When he fights the rogues, he is surprised at his ability, and thinks that his Dark Forest mentors will be proud of how well he fought.

Eclipse

 * When Lionpaw tells Tigerstar and Hawkfrost about the Prophecy, and says that is probably why he fights so well, they declare it nonsense. Tigerstar says that Lionpaw fights so well because of the training they give him, and that he should put any thoughts about a ridiculous prophecy out of his head, so that he won't be distracted.

Long Shadows

 * Lionblaze is still trained by the Dark Forest cats despite the fact that he is now a warrior.

Sunrise

 * Lionblaze confronts Tigerstar, now that he knows Squirrelflight and Brambleclaw aren't his real parents, asking why Tigerstar would train him if he wasn't his kin. Tigerstar says that he knew all along that Lionblaze was not his kin, and that this also proves that Lionblaze isn't a part of the Prophecy, so he should keep training with them to hone his skills further. Lionblaze angrily attacks Tigerstar, and they fight intensely. Lionblaze gets his claws at Tigerstar's throat, but lets him go. He vows to never return to the Dark Forest.

The Fourth Apprentice

 * When Jayfeather goes searching for Poppyfrost and finds her at the Moonpool, they are soon confronted by Breezepelt, who attacks them. He is helped by a Dark Forest cat who appears, although Jayfeather does not know who it is. He is helpless against them, until Honeyfern appears from StarClan to save him, and she fights them both off.
 * Later, at Poppyfrost's kitting, Tigerstar, Hawkfrost, and the Dark Forest cat (later revealed to be Brokenstar) appear and look at the kits. Jayfeather and Lionblaze tell them that they will never have the kits. The spirits disappear, but Jayfeather and Lionblaze grow worried that the Dark Forest is recruiting new cats, like Breezepelt, and perhaps Tigerheart, and maybe the Dark Forest is even planning a war on StarClan.

Fading Echoes

 * In the Prologue, Tigerstar, Hawkfrost, Brokenstar, Darkstripe, and Breezepelt are all practicing battle moves.
 * Later, Hawkfrost appears to Ivypaw in a field in a dream of hers. He casually offers to train her so she will be as good at hunting as Dovepaw, and she accepts. She believes him to be a StarClan cat, so she continues to let him train her.
 * Jayfeather, Spottedleaf, and Yellowfang later visit the Place of No Stars in search of answers. Yellowfang is too overcome with nervousness when she sees Brokenstar, so she goes back to StarClan. Spottedleaf and Jayfeather stay, and witness fierce battle training between Darkstripe, and two other Dark Forest cats, Snowtuft and Shredtail. Jayfeather is angered by the cruelty, but is powerless to stop it.
 * Then, Hawkfrost finally takes Ivypaw to the Dark Forest itself, and introduces her to the rest of the cats. She is nervous when meeting Tigerstar, as she has heard tales of his wickedness, but he convinces her that he didn't mean any harm, and was cruelly banished from ThunderClan for mere ambition. He then tells her that ShadowClan is supposedly planning to attack ThunderClan, and that she must convince Firestar to attack them first to protect their territory, which she does.

Known Residents
The spirits of the following cats are confirmed to reside in the Place of No Stars:
 * Brokenstar
 * Clawface
 * Darkstripe
 * Hawkfrost
 * Tigerstar
 * Snowtuft
 * Shredtail

The Place of No Stars likely hosts more spirits, but only the presence of the aforementioned ones was confirmed in the books.