The New Mutants
Professor X and several team members take an astral-plane tour of David's war-torn mind. The Prof learns he is David's father and meets two of his personalities.
Collects The New Mutants #26, 27, 28, 44, The Uncanny X-Men #253, 254, 255, 278, 279, 280 and X-Factor #69-70. Two arcs - New Mutants meet Legion, and the Shadow King besieges Muir Island.
Collects The New Mutants #13-31 and material from 4 other series. The New Mutants formative era - Demon Bear, Legion intro, and growing pains.
Collects New Mutants #1-35, Uncanny X-Men #160+, and Annuals. Claremont and McLeod launch Xaviers next generation, featuring the Demon Bear Saga.
Collects The New Mutants #25-34, X-Men Archives #1-3. New Mutants Classic -- Legion's debut and evolving team dynamics under Claremont.