Bluefur wonders what motivated Tigerstar to do everything that he did.
Tigerstar when he became an apprentice he was mentored by thistleclaw who was bloodthirsty and angry, and so Tigerstar became ambitious. This want for power was very dangerous, he tried everything to become deputy. All things he planned to do was ruined when Rusty/Firestar joined ThunderClan. Bluestar, his leader, only took notice of Firestar, who was Firepaw then. Firepaw-this, Firepaw-that! He needed something to get rid of young Firepaw. When Tigerstar became ShadowClan’s leader, he knew how to defeat Firestar, once and for all.
He half-trained a pack of dogs, and used a trail of dead rabbits to lead the dogs to the Thunderclan camp, then he killed Brindleface, Ashpelt and Fercloud’s mother, so that the dogs could get a taste of cat. This almost led to the destruction of Thunderclan, if it weren’t for Fireheart’s plan. They lured the dogs over the cliff and into the gorge. Unluckily, Bluestar fell in too. She lost her last life there, and just before, she knew that Tigerstar wouldn’t stop and she knew his danger.
Tigerstar tried to take over the whole forest next. He persuaded Riverclan first, then he brought Bloodclan, a loosely organized clan, whose leader was a cat named Scourge, to the forest. When Tigerstar revealed his full plan, Scourge turned on him and ripped all nine lives from him in one blow.
When he was dead, he sought out cats who were angry, or wanting to get power or vengeance on certain cats. Little did he know that his own mentor, Thistleclaw, had been trained in the dark forest. When he had enough cats, he trained them to not back down, and to kill cats, always, of course this is not what the warrior code allows. None of the cats seemed to notice this, and soon Tigerstar had a small group of warriors to help them fight against the clans. He was killed by Firestar, whom he hated to his last breath.
Part of this information comes from fandom because I want information that is true, not false. I hope this helps you guys if you are wondering, what Tigerstar’s past was and about his ambition.