From the introduction: The bottom sections of Dragon’s Delve have been repurposed so many times over the years (whether by the Mages Four or by Metterak) that it is often difficult to tell what a given level was originally for. Nowhere is this truer than on Level 18. This level is where the reality-altering powers of the Entropy Engine have had their greatest effect, causing the metaphysical barriers between our plane of existence and what are known as the “elemental planes” to be weak and constantly shifting. As a result, Level 18 finds itself under assault from a constantly shifting set of physical laws and atmospheric conditions.