The Devil was often worshipped by the people of Silent Hill by throwing up the horns in his name or by naming locations after him in hopes of attracting kids (kids love the devil) to the area. The Police in Silent Hill also happen to be 'down with the Devil' suggesting a town-wide conspiracy of sorts. This has resulted in many charming tourist attractions such as The Devil's Pit and the Cave of Tears.
Originally conceived as a result of Tour Guide Nixon in the Silent Hill Downpour Let's Play, the Devil has become a running gag in the series parodying 'edgy' advertising because, as all pensioners and marketing agents know, kids just fucking love themselves some Beelzebub. Allegiance to the Devil can apparently be expressed by 'throwing up the horns' and listening to Bon Jovi and the Beastie Boys. It is also commonly known that the Devil is a poor tenant when it comes to paying much rent.