Banshee has recommended a number of rare components that you should be able to use to restore your ruined Thorn to working order. First on the list is Hadronic Essence, a dense lattice of exotic baryons and mesons, once commonly favored as an infusion in Warlock fieldweave. Gather Hadronic Essence by completing bounties for Asher Mir on Io, by defeating Warlocks in the Crucible, or by completing Nightfall strikes. Nightfall strikes grant the most efficient progress.