OSR Advanced Player Options

The OSR Advanced Player Options books compile several years of material into a single book designed to expand any OSR-style game. Written for Old School Essentials, it contains the following:

Guidelines for running successful play-by-post games.
A simple skill system.
Rules for founding temples and using the divine energy that worship generates.
Rules for improving magical weapons by performing feats of derring-do.
A simple prestige class system based on rules from the BECMI Gazetteers
A bunch of new race-as-class options, including binder (from 3.x Tome of Magic), monk, necromancer, parrot-folk, and more.
Rules for researching spells and creating magical items.
Rules for ritual spells.
Dozens of new spells.