Nathan Long
Manslayer
Gotrek & Felix (series) part 9

Gotrek and Felix are reunited with an old friend and plunged once again into deadly conflict against the forces of Chaos. But with saboteurs at work aboard the airship on which they travel, they must discover a traitor before they die ignominiously.
Warhammer
novel

Also in:
Gotrek & Felix: the Third Omnibus
Gotrek & Felix: the Complete Journey