Doug Ramsey is first mentioned in Uncanny X-Men (1st series) #177. His codename was first mentioned (rather randomly) in New Mutants (1st series) #34.
Cypher was killed in New Mutants (1st series) #60, when he lept in front of a bullet to save Wolfsbane. He was one of countless mutants reanimated by Eli Bard using the transmode virus at the behest of Selene in X-Force (3rd series) #18. Doug managed to purge the controlling influences in his system and return fully to life in New Mutants (3rd series) #8.