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In January 2012, Wizards of the Coast announced that a new edition of the game, at the time referred to as D&D Next, was under development. In direct contrast to the previous editions of the game, D&D Next was developed partly via a public open playtest. An early build of the new edition debuted at the 2012 Dungeons & Dragons Experience event to about 500 fans. Public playtesting began on May 24, 2012, with the final playtest packet released on September 20, 2013.
The 5th edition's Basic Rules, a free PDF containing complete rules for play and a subset of the player and DM content from the core rulebooks, was released on July 3, 2014. The Starter Set was released on July 15, featuring a set of pre-generated characters, a set of instructions for basic play, and the adventure module Lost Mine of Phandelver. The Player's Handbook was released on August 19, 2014. The fifth edition Monster Manual was released on September 30, 2014. The Dungeon Master's Guide was released on December 9, 2014. The edition returns to having only three core rule books, with the Player’s Handbook containing most major races and classes.
Mechanically, 5th edition draws heavily on prior editions, while introducing some new mechanics intended to simplify ease of play. Actions are now more dependent on checks made with the six core abilities with skills taking a more supportive role.
Skills, weapons, items, saving throws and other things that a character is trained in (proficient) now all use a single proficiency bonus that increases as level increases. Multiple defense values have been removed, returning to a single defense value of armor class and using more traditional saving throws. Saving throws are reworked to be situational checks based on the six core abilities instead of generic d20 rolls. Feats are now optional features that can be taken instead of core ability score increases and are reworked to be occasional major upgrades instead of frequent minor upgrades.
The “advantage/disadvantage” mechanic was introduced, streamlining conditional and situational modifiers to a simpler mechanic: rolling two d20s for a situation and taking the higher of the two for “advantage” and the lower of the two for “disadvantage” and cancelling each other out when both apply.
The power system of 4th edition has been removed, replacing them with more traditional class features that are gained as characters level. Each spell-casting class uses a unique system to cast their spells, with wizards and clerics using a slightly modified version of the spell preparation system of previous editions. Healing Surges are replaced by Hit Dice, requiring a character to roll a hit die during a short rest instead of healing a flat rate of hit points.