Old-School Essentials is a modular game where the core rules of the game are extended by additional "rules modules" which add content for different genres of fantastic adventure. The Old-School Essentials Rules Tome is a compilation of the core rules plus four rules modules, forming a complete game for Classic Fantasy adventures:

During a Blood Moon, the halls of an extra-dimensional vampire phase into the material world. Local people are dragged to the accursed halls, snatched up for the bloody pleasure of the vampiric Blood King. A horror themed adventure for Old-School Essentials! Designed for characters of level 3-5. Written by Diogo Nogueira and illustrated by Justine Jones.