GOG and Steam are both getting into the Halloween spirit with sales going on this week. Steam's sale is centered around spooky/horror games, while GOG's is more of a general catch all. There are some decent discounts to be had, so head over to Steam before November 1 and GOG before November 5 to catch the sales.
https://www.notebookcheck.net/Get-spooked-this-Halloween-with-Halloween-sales-courtesy-of-GOG-and-Steam.350726.0.html