From Underground

A third-party monster manual for Old-School Essentials and other old-school fantasy role-playing games, featuring creatures and factions that dwell underground. Its entries include fungal trolls, cave-haunting spirits, a criminal gang of floating eyeballs, and a cult devoted to a flaming green skull, with details and hooks for use in adventures.

属性／ステータス制（STR、CON、PERなど）レベル制（XPを獲得してレベルアップ）クラス制（パイロット、ウィザード、サイエンティストなど）