"TigerClan was the name of one of the great Clans of ancient times. Tigerstar has no right to use it now. Nor does he have the right to change the number of Clans in the forest. We have lived as four Clans for innumerable seasons, following the warrior code laid down for us by StarClan. To throw aside our ancient ways would bring disaster. I'll die before I join my Clan to yours!"
An alliance formed between ShadowClan and RiverClan because of the leader Leopardstar's affection towards Tigerstar, and the two joined at Tigerstar's instigation to form TigerClan. He claimed that it would help the four Clans to join together because they could share prey and work together as joint leaders. Tallstar disagreed, because TigerClan was the name of one of the Great Clans, and Firestar disagreed, knowing that Tigerstar would never share power equally, though he claimed the four Clans would have equal power. However, it was Tigerstar's Clan, ShadowClan, that held most of the power; a few ShadowClan warriors were left at the RiverClan camp permanently, where they did little work for Leopardstar's Clan, just eating their prey and never hunting for themselves; instead, just keeping an eye on them to ensure loyalty. There, Tigerstar built a mound of bones known as the Bonehill where he addressed the joint Clan, in an imitation of the Highrock of his former Clan, ThunderClan.
Tigerstar soon began a purge of half-Clan cats; he pitted the underfed Stonefur, former deputy of RiverClan, against Darkstripe, a traitor to ThunderClan who left it to follow Tigerstar to ShadowClan. Despite being better-fed and more rested, Darkstripe was nearly defeated by Stonefur until Tigerstar's deputy Blackfoot intervened, killing Stonefur. Though they planned to do the same to Stonefur's sister Mistyfoot, and the kits of Graystripe and Silverstream, Stormpaw and Featherpaw, a trio party from ThunderClan consisting of its leader, Firestar, Graystripe, and the lonerRavenpaw rescued the cats before TigerClan could do so, narrowly escaping a group of the merged Clan's cats on their way back to ThunderClan territory. Tigerstar was undaunted, though, and allied with BloodClan, a group of cats who lived in Twolegplace in hopes of forcing his enemies out of the forest or into TigerClan.
Tigerstar didn't count on BloodClan's leader, Scourge, though. Scourge killed Tigerstar when he attacked him, attempting to make him obey his order to attack the Clans. With the loss of their leader, TigerClan was finished. Firestar persuaded Leopardstar, the Clan's new leader, to join her forces with his newly-formed LionClan to battle BloodClan, now attempting to drive all of the cats from the forest and take it for themselves. With the death of Scourge at the claws of Firestar and the defeat of BloodClan, LionClan disbanded, and the state of the four Clans returned to normal.