Boulder

Boulder is a skinny, silver tabby tom with a ragged ear and bright, watchful eyes.

Into the Wild

 * He was a friend and rogue follower of Brokenstar, and was one of the warriors in his circle of "elite warriors". When Firepaw, Yellowfang, Whitestorm, the ShadowClan elders and ThunderClan patrol came to rescue the kits, Firepaw defeated him, sending him running into exile. Wetpaw is his apprentice.

A Dangerous Path

 * When Tigerstar became leader, Boulder was brought back into ShadowClan along with Russetfur, Blackfoot, and Jaggedtooth He was welcomed among them.

The Darkest Hour

 * In the prologue, he and Tigerstar went into BloodClan territory so Tigerstar could meet Scourge. When Scourge killed Tigerstar, Jaggedtooth joined BloodClan, and Boulder thought it was worth betraying BloodClan so he could get his claws in Jaggedtooth's fur. He fought alongside LionClan (the four Clans combined, led by Firestar) to fight BloodClan.

Into the Woods

 * He is introduced by Tigerstar to Sasha, a rogue, as one of his "best fighters". He is seen again a day after Sasha came to the ShadowClan camp, and when he, Tigerstar, Oakfur, and Sasha went on a border patrol. He is also seen planning with Tigerstar and some other warriors near the end of the book.

The Rise of Scourge

 * He is seen with Tigerstar in BloodClan.

Midnight

 * Boulder does not formally appear in Midnight, but is listed in the allegiances.

Dawn

 * He is now an elder of ShadowClan. When the Clans are deciding where to go, Blackstar says ShadowClan is going to BloodClan's former home, and that one of their elders, Boulder, used to be a member of BloodClan and can show the way.

The Sight

 * Leafpool gets news from Littlecloud that ShadowClan has lost an elder due to greencough, which could have been Boulder, as he doesn't appear in later books.

Secrets of the Clans

 * Boulder gives the tour of the ShadowClan forest camp, he talks about the boggy ground, prey and camps of ShadowClan. He also explains he was a loner before he met a ShadowClan warrior who tempted him into the life of the clans, not mentoning his ties with BloodClan.

Cats of the Clans

 * Rock tells the kits of StarClan how Boulder was raised in BloodClan, but came to the forest when he heard of how much safer and easier the system of territories, warriors, and patrols sounded. He apparently had too much faith in the Warrior Code. He was the cat who led Tigerstar to Scourge, with a desire to impress his new leader, without realizing that he knew from his time in BloodClan that Scourge would never help Tigerstar win a battle then leave with the promise of some small hunting grounds. According to Rock, Boulder was not an evil cat. His ambition just got the better of him. He thought everything would work out as Tigerstar had planned, with BloodClan helping to take over the forest, and less cats would be hurt if the takeover was smoother.