With the launch of the fifth edition of Dungeons & Dragons, the designers hosted panels at Gen Con 2014 introducing the game to new and returning players. You can listen to designers Rodney Thompson and Greg Bilsland at one of these sessions recorded by the Tome Show Podcast.

During the discussions, the designers listed 5 new or different things in the new edition. This post recaps that list.

First though, the designers explained the game’s core: Whenever a character’s action has an uncertain outcome, you roll a twenty-sided die (d20), add a bonus, and try to reach a target number. If your roll plus your bonus equals or exceeds the number, you succeed. In the game, players make three types of d20 rolls following this mechanic.

• When your character tries to strike an enemy in combat, an attack roll determines whether the attack hits. To succeed, an attack roll must equal or exceed a foe’s armor class.
• When your character attempts a task with a chance of failure, an ability check determines success. To succeed, an ability check must equal or exceed a difficulty class.
• When your character resists a spell, trap, poison, disease, or similar danger, a saving throw determines whether the character succumbs. To succeed, a saving throw must equal or exceed a difficulty class.

As players make these d20 rolls on behalf of their characters, the dungeon master makes these rolls for the monsters.

These mechanics existed in earlier editions, but the fifth edition makes five, key additions:

1. Advantage and Disadvantage

When something in the game world improves your chance of hitting, succeeding at a task, or avoiding a threat, you gain advantage on your d20 roll. When you have advantage, you roll two twenty-sided dice and use the highest of the two die rolls. For example, when your foe cannot see you and properly defend, you might gain advantage on an attack . Similarly, when circumstances hurt your chance of success, you suffer disadvantage. When you have disadvantage, you roll two d20 and use the lowest of the two rolls.

Advantage and disadvantage don’t multiply. Even if you gain advantage from more than one source, you never roll more than two d20 dice. You cannot stack advantages. Likewise, If you suffer disadvantage from two sources, you still just roll two d20 and take the lowest. If you both gain advantage and suffer disadvantage on the same roll, they cancel and you roll one d20. Any number of sources of advantage and disadvantage cancel each other out, leading to rolling one d20. This spares players from having to count advantages and disadvantages.

Advantage and disadvantage replace most of the pluses and minuses that appeared in earlier editions, but the mechanic does not apply to cover. A target with half cover gains a +2 bonus to AC and dexterity saving throws. A target with three-quarters cover gains a +5 bonus to AC and dexterity saving throws. For more on this design choice, see “How cover and tool proficiency reveal choices in fifth-edition design.”

Reason for change. Third-edition D&D featured long lists of pluses and minuses that applied when the situation affected an attack or check. While these modifiers added realism, they slowed play, seldom made a difference, and were often overlooked. Fifth edition drops all the fussy calculation for advantage and disadvantage. While less of a simulation than a tally of pluses, the new mechanic plays quickly and eliminates math and memory demands.

2. Spellcasting and spell slots

Except for Rangers and Paladins, every spellcaster knows a number of cantrips. Cantrips can be cast at will, as often as desired. More powerful spells cost spell slots to cast.

Every spellcaster has a number of spell slots they spend to cast spells. As Rodney Thompson explains, slots are the fuel characters burn to cast spells. Spell slots have a level and you can spend them to cast a spell of equal level or lower. For example, you can spend a second-level slot to cast either a first or second level spell.

Many spells become more powerful when cast with a higher-level spell slot. For example, the first-level Magic Missile spell shoots another missile when cast with a second-level slot. Unlike in third edition, spells never grow more powerful simply because a higher-level caster throws them. Only spending a higher-level slot boosts their power.

Characters regain spell slots after a long rest.

Preparing spells. Characters in most classes must prepare spells before they can cast them. When you cast a spell, you spend a spell slot, but the spell remains prepared. Unlike in earlier editions, you can cast a prepared spell more than once, as long as you still have slots to spend. After a long rest, you can change the spells you have prepared.

Bards, Sorcerers, and Warlocks don’t prepare spells. They know spells that they can cast whenever they have slots to spend. You choose which spells your character knows as you gain levels.

Reason for change. This system grants casters an extra measure of flexibility. It spares players the risk of preparing spells that prove useless, resulting in a bad day of adventure.

3. Concentration

Many spells require their caster to maintain concentration to keep their magic going. These spells list durations such as “Concentration, up to 1 minute,” meaning that if the caster concentrates, the spell lasts a minute.

Losing concentration. A spellcaster can concentrate on just one spell at a time. You can cast other spells that do not require concentration without breaking concentration. You can end concentration on a spell at any time, without an action. This ends the spell’s effects, but lets you cast a new spell that demands concentration.

When casters maintaining concentration take damage, they must make a Constitution saving throw to keep their spell going. The DC equals 10 or half the damage suffered, whichever is higher.

Combining magical effects. When different spells’ overlap, the effects add together. The effects of the same spell cast multiple times don’t combine. Only apply the one spell with the most potent effect, such as the highest bonus. If that spell ends, then less potent spells may show their effects.

Reason for change. In earlier editions, higher-level parties might enter a fight blanketed with spells like Haste, Invisible, Fly, Blur, Polymorph Self, Resist Elements, and on and on. Players needed spreadsheets to track their bonuses, while the DM struggled to create any challenge. Then when the evil mage casts dispel magic, buffs disappear and all the numbers need recalculation. Concentration simplifies the game by limiting the magical effects in play.

Concentration forces the min-maxers to search harder for broken combinations of spell effects. Multiple spell casters can still combine effects, but the designers see this as teamwork, not as a single character dominating the game.

Concentration also opens tactical options. Casters become targets for foes aiming to break concentration and stop spells. For more, see “Fifth-edition D&D strategy for fourth-edition players: Kill the wizard.”

Not all spells with durations require concentration. A few spells such as Mage Armor, Mirror Image, and Fire Shield offer protection without concentration.

4. Proficiency

Characters have proficiency in the things they do well. A character can be proficient in armor, skills, saving throws, weapons, and tools.

Proficiency grants a bonus to the d20 rolls you make for attacks, saving throws, and checks. The proficiency bonus starts at +2 at level 1 and rises to +6 at level 19. Proficiency appears throughout the system.

• When characters are proficient with a weapon, they add their proficiency bonus to the attack roll. When characters lack proficiency, they do not gain this bonus.
• When characters cast a spell that requires an attack roll, they add their proficiency bonus to the roll. Spellcasters always gain proficiency with spells they can cast.
• When characters make an ability check covered by one of their skills, they add their proficiency bonus to the check.
• When characters are proficient with tools used to make an ability check, they add their proficiency bonus to the check. You never add a proficiency bonus for both a skill and a tool to the same check.
• When characters are proficient with a type of saving throw, they add their proficiency bonus to those saves.

Proficiency with armor works differently from proficiency with everything else. Rather than granting a proficiency bonus, armor proficiency grants the ability to wear armor without disadvantage. This difference may confuse new players, but earlier editions handled armor proficiency in a similar manner.

Reason for change. Earlier editions of D&D featured countless tables showing bonuses for attack rolls and saving throws, and added additional bonuses for skills and proficiencies. The fifth-edition proficiency bonus simplifies by sweeping all these tables and rules into a single rising bonus. For more, see “How D&D Next moves toward a simpler core game” and “Proficiency and bounded accuracy in D&D Next.”

5. Bonus actions

Characters take just one action on their turn. Some class features, spells, and other abilities let you take an additional action called a bonus action. Three key limitations apply to bonus actions.

• To gain a bonus action, something like a special ability or spell must state that you get a bonus action to do something. Otherwise, you get no bonus action. For example, when you take an attack action to attack with a light melee weapon in one hand, you can use a bonus action to attack with a second light melee weapon in your other hand.
• You can only take one bonus action. For example, at second level, the Rogue’s Cunning Action class feature grants a bonus action to Dash, Disengage, or Hide. If your rogue also wields two weapons, then you must choose between using your one bonus for your Cunning Action or for a second weapon strike.
• You can only take bonus actions on your turn. For example, your rogue cannot interrupt another turn to take the bonus action granted by Cunning Action.

Reason for change. Fourth-edition characters could gain numerous extra actions, which helped the game earn a reputation for long turns. Bonus actions speed play by limiting the number of extra things someone can do during a turn.