The Slayers Club is Bethesda.net's "official fan-club" for the Doom series. Connecting games to one's Bethesda.net account (an option available in the 2019 re-edition of Doom and Doom II and of Doom 3, the 2020 re-edition of Doom 64, Doom (2016), and Doom Eternal so far) allows to earn "points" by playing and unlocking achievements. Reading articles on the Slayers Club website also yields points. Further points can be earned by participating in weekly or monthly challenges organized by the Club.
These points allow to climb in rank (currently the highest rank is the 15th, "Doom Slayer", at 13 000 points), which unlocks cosmetic options in games (only Doom Eternal so far) and discount coupons on official Doom merchandise at the site's shop.