Conversation so far:
What led to Kai Hansen and Michael Kiske's departures from Helloween?
Guitarist Kai Hansen unexpectedly left the band in 1989.
Why did Michael Kiske leave Helloween?
Conflicts within the rest of the band worsened, with Michael Weikath refusing to work any longer with Michael Kiske. The decision was made to fire Kiske.
Did Kai Hansen give a reason for leaving Helloween?
Kai Hansen left due to ill-health, conflicts within the band, troubles with Noise International, and a growing dissatisfaction with life on tour.

Question: Who replaced Hansen?
Self-contained rewrite: Who replaced Kai Hansen in Helloween?