Boulder

Boulder is a skinny gray tom with a ragged ear.

Into the Wild

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

A Dangerous Path

 * When Tigerstar became leader, Boulder was brought back into ShadowClan.

The Darkest Hour

 * In the prologue of The Darkest Hour, 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.

Dawn

 * In The New Prophecy, he was an elder. However, he didn't appear in the allegiances until Dawn. When the Clans are deciding where to go, Blackstar says ShadowClan is going to BloodClan's former home, and that one of their elders, likely Boulder, used to be a member of BloodClan and can show the way.

Sunset
He is still an elder of ShadowClan.

The Sight
Leafpool gets news from Littlecloud that Shadowclan has lost an elder due to Greencough, which could've been Boulder.