Originally Posted by
AmonGwareth
Different categories of monsters drop specific classes of loot. So, as hallucin8 said formulas drop from Semi-Intelligents (Skulks, Ogres, Pygmies, etc), Undead and Chests. Formulas are considered rare loot, however, so you will only get them from monsters in the "upper-half" of a Tier (so level 11-20 for T1, 31-40 for T2, etc). Also, formulas are split between those in the "lower-half" of the Skill range and those in the "upper-half". So, for example, Formulas that can be scribed by players that are generally T1 will be on T1 monsters, while those which generally required players to be T2 will drop from T2 monsters. Hope that makes sense.