Post by Peter Watson-Wailes

LemonLord7 and Ripper62 from Reddit compiled these a large set of clarifications to and lesser-known rules. I thought I'd organise the list, find the sources and tidy up the answers a little. Hopefully you'll find it a useful resource for next time there's an debate.

Spells

  • Many spells can only target creatures and not objects - check what they can act on. Also, objects are immune to poison and psychic damage, but otherwise they can be affected by physical and magical attacks much like creatures - PHB p185, Interacting with Objects
  • Readying a spell requires concentration until the casting or the beginning the next turn, and expends the spell slot whether or not it casts - PHB p193, Ready
  • Roll once only for spells affecting multiple creatures. The rolled damage is applied to every target - PHB p196, Damage Rolls
  • Casting a spell as a bonus action means you can only cast cantrips for the rest of your turn - PHB p202, Bonus Action. Note it's a bonus action, and not casting two spells. If you have Action Surge, then you can cast two spells in one turn, since no bonus action is used to do so
  • Not all spellcasters can cast spells as rituals - PHB p201-202, Rituals
  • Charmed targets can't attack the charmer or target them with harmful abilities or spells - PHB p290, Charmed

Attacks

  • When an Attack of Opportunity happens on someone else's turn, a rogue's Sneak damage can be applied, but a fighter's Extra Attack cannot. The same applies to readied actions. PHB p96, Sneak Attack (Once per turn, you can deal an extra 1d6 damage to one creature you hit with an attack)
  • Action Surge does not give a bonus action; it's just poorly worded. A better wording would be "On your turn, on top of your regular action (and possible bonus action), you can take one additional action. PHB p172, Action Surge
  • A round is one turn from every combatant. A turn is when one combatant/group of combatants acts in the round. PHB p189, The Order of Combat
  • Attacks of Opportunity happen prior to a creature moving out of your reach, Readied Actions happen after a trigger. PHB p195, Opportunity Attacks & PHB p193, Ready
  • Half cover gives a +2 to both AC & DEX saves. 3/4 cover increases this to +5, unless attacker has the Sharpshooter or Spell Sniper feats. PHB p196, Cover
  • Attacks with nets are always made with disadvantage, unless fighting underwater. This link & PBH p198, Underwater Combat

Combat

  • All enemy NPCs of the same type have the same initiative. PHB p189, Initiative
  • If an opponent is within melee range, you suffer disadvantage when making any ranged attack, not just targeting the melee-opponent. This doesn't apply if the enemy is incapacitated. PHB p195, Ranged Attacks in Close Combat
  • Resistance and then vulnerability are applied after all other modifiers to damage. Also, round different types of damage individually; e.g., if you are hit with Flame Tongue and suffer 9 slashing and 7 fire damage, and you have Resistance to both, you round down each separately. PHB p197, Vulnerability
  • You can take your reaction on your turn; e.g., counterspelling Counterspell - see this Sage Advice column
    • Extra Attack only grants additional attacks when you take the attack action on your turn. If you ready an action to attack, you can only make 1 attack, unless your trigger occurs before you end your turn. PHB p49, Extra Attack

Feats

  • Since Jack of All Trades works with all ability checks, and in 5e all checks are ability checks, this includes initiative rolls and spells like Counterspell. PHB p54, Jack of All Trades & p174, Ability Checks

Rests

  • You can only have 1 long rest per 24 hours. Taking a second long rest just means you're rested. Also, a long rest can be interrupted by up to an hour of activities (combat, casting spells, travelling etc), or 2 hours of light activity (talking, eating etc) and still give the benefits it should. PHB p186, Long Rest

Advantage & Disadvantage

  • Causes don't stack - you either have it or your don't, and having both means you get neither, irrespective of how many of each you have. PHB p173, Advantage and Disadvantage
  • Darkness/fog provide cancel out advantage and disadvantage if both targets can't see each other (you can't aim, they can't see it coming) due to using the rules for Blindness. PHB p183, Vision and Light & PHB p290, Blinded
  • Each gives +/-5 respectively to passive checks. These bonuses do not stack. PHB p175, Passive Checks
  • Frightened imposes disadvantage on all attacks and ability checks. The sufferer can't move closer to source of fear, whilst they have Line of Sight to it. PHB p290, Frightened

Resources

  • Harvesting poison from a creature is a DC20 Intelligence (Nature) check. DMG p258, Crafting and Harvesting Poison
  • Component pouches aren't standard equipment. Buy one if you'll need it

Other

  • If you have Darkvision, treat darkness as dim light (disadvantage on perception checks involving sight and -5 to passive perception). PHB p23, Elf Traits
  • Get exactly the character background you want using the Custom Background rules on page 125 of the PHB
  • Taking damage due to falling automatically knocks a faller prone. Also, damage from falling caps at 20d6, and stacks by 1d6 for every 10 feet. PHB p183, Falling
  • Moving through another creature's space is always treated as difficult terrain - PHB p191, Difficult Terrain
  • A rolled 1 is only an automatic failure for attack rolls. There are no critical fails or successes on skill checks. The only slight exception is Death Saving Throws, where a 1 counts as two failed saving throws. PHB p194, Rolling 1 or 20
  • Unless specified, always round fractions down. PHB p7, Round Down
  • Perception checks can't be less than a character's Passive Perception - http://dnd.wizards.com/articles/features/james-haeck-dd-writing - 15:30 onwards. Also see this link

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