System Reference Document 5.2.1
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Adventurers can’t spend every hour adventuring. 
They need rest. Any creature can take hour-long 
Short Rests in the midst of a day and an 8-hour Long 
Rest to end it. Regaining Hit Points is one of the main 
benefits of a rest. “Rules Glossary” provides the 
rules for Short and Long Rests.
Controlling a Mount
You can control a mount only if it has been trained 
to accept a rider. Domesticated horses, mules, and 
similar creatures have such training.
 The Initiative of a controlled mount changes to 
match yours when you mount it. It moves on your 
turn as you direct it, and it has only three action op -
tions during that turn: Dash, Disengage, and Dodge. 
A controlled mount can move and act even on the 
turn that you mount it.
 In contrast, an independent mount—one that lets 
you ride but ignores your control—retains its place 
in the Initiative order and moves and acts as it likes.
Falling Off
If an effect is about to move your mount against its 
will while you’re on it, you must succeed on a DC 10 
Dexterity saving throw or fall off, landing with the 
Prone condition (see “Rules Glossary”) in an unoc -
cupied space within 5 feet of the mount.
 While mounted, you must make the same save if 
you’re knocked Prone or the mount is.
Underwater Combat
A fight underwater follows these rules.
Impeded Weapons
When making a melee attack roll with a weapon 
underwater, a creature that lacks a Swim Speed has 
Disadvantage on the attack roll unless the weapon 
deals Piercing damage.
 A ranged attack roll with a weapon underwater 
automatically misses a target beyond the weapon’s 
normal range, and the attack roll has Disadvantage 
against a target within normal range.
Fire Resistance
Anything underwater has Resistance to Fire dam -
age (explained in “Damage and Healing”).
Damage and Healing
Injury and death are frequent threats, as detailed in 
the following rules.
Hit Points
Hit Points represent durability and the will to live. 
Creatures with more Hit Points are more difficult 
to kill. Your Hit Point maximum is the number of 
Hit Points you have when uninjured. Your current 
Hit Points can be any number from that maximum 
down to 0, which is the lowest Hit Points can go.
 Whenever you take damage, subtract it from your 
Hit Points. Hit Point loss has no effect on your capa-
bilities until you reach 0 Hit Points.
 If you have half your Hit Points or fewer, you’re 
Bloodied, which has no game effect on its own but 
which might trigger other game effects.
Damage Rolls
Each weapon, spell, and damaging monster ability 
specifies the damage it deals. You roll the damage 
dice, add any modifiers, and deal the damage to 
your target. If there’s a penalty to the damage, it’s 
possible to deal 0 damage but not negative damage.
 When attacking with a weapon, you add your abil -
ity modifier—the same modifier used for the attack 
roll—to the damage roll. A spell tells you which dice 
to roll for damage and whether to add any modi -
fiers. Unless a rule says otherwise, you don’t add 
your ability modifier to a fixed damage amount that 
doesn’t use a roll, such as the damage of a Blowgun. 
See “Equipment” for weapons’ damage dice and 
“Spells” for spells’ damage dice.
Critical Hits
When you score a Critical Hit, you deal extra dam -
age. Roll the attack’s damage dice twice, add them 
together, and add any relevant modifiers as normal. 
For example, if you score a Critical Hit with a Dag -
ger, roll 2d4 for the damage rather than 1d4, and 
add your relevant ability modifier. If the attack in -
volves other damage dice, such as from the Rogue’s 
Sneak Attack feature, you also roll those dice twice.
Saving Throws and Damage
Damage dealt via saving throws uses these rules.
Damage against Multiple Targets
When you create a damaging effect that forces two 
or more targets to make saving throws against it at 
the same time, roll the damage once for all the tar -
gets. For example, when a wizard casts Fireball, the 
spell’s damage is rolled once for all creatures caught 
in the blast.
Half Damage
Many saving throw effects deal half damage (round 
down) to a target when the target succeeds on the 
saving throw. The halved damage is equal to half 
the damage that would be dealt on a failed save.
Damage Types
Each instance of damage has a type, like Fire 
or Slashing. Damage types are listed in “Rules 