The "Player's Handbook" for 2nd edition was compatible with 1st edition rules, but was streamlined and clarified. The book included information on how to play the standard character classes: warriors (including fighters, paladins, and rangers), wizards (including mages and specialist wizards such as illusionists), priests (clerics and guidelines for variance by mythos, including the druid as an example), and rogues (including thieves and bards); while most character classes remained about the same as in the 1st edition rules, the bard was regularized, and the assassin and monk were dropped. TSR, Inc. also removed some races from the game, such as half-orcs, although some of these were added back into the game in supplements, such as "The Complete Book of Humanoids". Optional rules for skills, known as "proficiencies", were added, and sections describing role-playing, combat, magic, time and movement, equipment, and spell descriptions were all expanded. The book included major changes regarding character classes, races, and magic, and incorporated many new rules that had been published in supplements such as "Unearthed Arcana" and "Dragonlance Adventures".