For those who have already dived into the dark caverns of D100 Dungeon and feel the rule book is getting thin, D100 Dungeon: The Lost Tome of Extraordinary Rules arrives like a true treasure chest. This printable supplement brings over 100 new rules, tables, and mechanics that fit right into the familiar flow of the base game. Among the additions is Beast Mastery, which lets you tame and use pet companions, and the Artisan system, expanding crafting to create unique items from collected materials. Mapping is also friendlier thanks to the New Mapping Table, which uses standard square areas to make corridors and rooms easier to visualize.

Additionally, the book introduces new hero paths such as the Arcanist and Champion, each unlocking unique abilities and gear. The Easier Investments table offers a quicker way to invest resources in long‑term projects, while the Combat Experience table rewards players who excel at monster slaying. Special Blue areas become lairs and challenges, and Treasure Table D reveals rare items found in those spots.

D100 Dungeon: The Lost Tome of Extraordinary Rules works with six‑sided dice, paper, and pencil, and is ideal for 1 to 4 players. Playtime can range from 5 to 90 minutes, depending on how many rules and tables you use. While the supplement is rich and detailed, its complexity can be a bit high for newcomers to the D100 Dungeon universe, but for veterans looking to deepen the experience, the book is a valuable and fun addition.