Slain: Back from Hell is now live on GOG.com
All existing GOG customers will receive a free gifting code too. Go to Slain: Back From Hell in your library and click on the box for a message that contains your gift code.
https://www.gog.com/game/slain
PS
Apologies for posting about GOG on here guys but since we have had a good number of requests about the GOG version on updates and patch notes on here I thought it made sense!