Crossovers/Events/Major Stories:
#8 - first appearance of Magma
#9 - first appearance of Selene
#14 - Magik joins New Mutants
#16-17 - Hellions
#18-20 - Demon Bear Saga
#18 - first Warlock
#21 - Warlock and Cypher join the team
Annual #1 -first Lila Cheney
#26 - first Legion
#29 - first Strong Guy
#30, #36-37 - Secret Wars II crossover
Spiecial Edition #1 – Asgardian Wars crossover with Uncanny X-Men Annual #9; first Brightwind, Mirage becomes a Valkyrie
#35 – first Magneto as headmaster
Annual #2 - Psylocke joins the X-cast
#46 - Mutant Massacre
#47-50 - lost in time
#51 - Magneto joins the Hellfire Club
#57 - first appearance of Bird Brain
#59-61 - Fall of the Mutants, Cypher dies
#71-73 - Inferno , Magik is reduced to a child
#75 – split with Magneto
#76 - New Mutants merge teams with the X-Terminators
#84-86 - Acts of Vengeance
#87 - first Cable
#95-97 - X-Tinction Agenda
#98 - first Deadpool, first Gideon, death of Emmanuel daCosta
#99 - first Shatterstar, first Feral, Thdunerbird II becomes Warpath
#100 - final issue