You hate the sun and extended move.
When the PC has the effect of corruption: You hate the sun and try to blot it.
The corruption will somtimes activate while the PC is moving after the extended move command 'w[1346789]' was issued. The PC then moves either one tile or to the edge of the darkened area.
This can and has the effect that the PC can un-intentionally move into another character under darkness and attack it. Not favourable to attack your own companion as happened to me. Or dwarfs in Dwarftown.
I'm assuming that it will neither stop the PC from moving into water.
The extended movement has to stop when the darkness is vomited. Is my suggestion.