While you were speaking to Tyra, she mentioned something called the Hated Path, a sort of primer to transform an ordinary Hand Cannon into a Thorn. Bathe your Light in horrors. Feed your weapon with death. Bind it with sickness. Horrors, death, sickness… that all sounds like the Hive nests on Titan to you. Defeat the Arbiters, Sardav and Telesh, then defeat Savathûn's Song in an epic reprise of strike "Savathûn's Song" on Titan.