In Uncanny X-Men #260 from 1990, pilot Cylla Markham, a friend of Banshee's, was badly hurt and in Uncanny X-Men #261 that same year, she accepted an offer from Donald Pierce to become one of his cyborg Reavers. In Uncanny X-Men #269, also from 1990, he made her into his new Skullbuster, replacing the one who had died in Uncanny X-Men #255 in 1989. Claremont didn't get to introduce the finished result before leaving the series, but in Wolverine vol.2 #55-57 from 1992, writer Larry Hama introduced a cyborg created by Donald Pierce that went by the name Cylla. This cyborg bore no resemblance to the new Skullbuster and was killed off in Wolverine vol.2 #78 in 1994. Then, the original Skullbuster reappeared without explanation in the 1997 Domino mini-series written by Ben Raab.
When Claremont returned to Marvel, Cylla Markham finally debuted as the new Skullbuster in X-Treme X-Men Annual 2001, ignoring what had happened in between his stints as X-Men writer.
In Uncanny X-Men #262 in 1990, Donald Pierce sent his Reavers after his former Hellfire Club colleague Emma Frost, but they never caught up with her. Claremont was building up to a final confrontation between the Reavers and the X-Men, which never happened, because subsequent writer John Byrne had the Upstart Trevor Fitzroy's Sentinels kill off all the Reavers, except Lady Deathstrike and Cylla Markham, in Uncanny X-Men #281 in 1991. All of them were revived for the X-Treme X-Men 2001 annual, though.