Tigerstar trained Hawkfrost and his half-brother, Bramblestar, in their dreams, nurturing their ambition, trying to have them take over the whole forest. Hawkfrost had unwavering loyalty to his father, which was missing in Bramblestar. Hawkfrost also planned with Ashfur to lead Firestar into a twoleg fox-trap. Firestar would've died if Bramblestar didn't ruin everything. He freed Firestar and killed Hawkfrost instead.
In the Dark Forest, Hawkfrost found out Ivypool, whom he was very proud of. She showed great promise and seemed perfectly loyal. He was very angry with her when he found out that she had lied the whole time. He tried very hard to kill her, but failed, because Hollyleaf came in to intercept the blow. He killed her, but also went streaming away from them. Later, he tried to attack Firestar, but Bramblestar ended up killing him a second time, banishing him forever.