Thieves & Kings
A short rest is a period of downtime, at least one (1) hour long, during which a character does nothing more strenuous than eating, drinking, reading, and tending to wounds. A character can spend one or more Hit Dice at the end of a short rest, up to the character’s maximum number of Hit Dice, which is equal to the character’s level. For each Hit Die spent in this way, the player rolls the die and adds the character’s Constitution modifier to it. The character regains hit points equal to the total. The player can decide to spend an additional Hit Die after each roll. A character regains some spent Hit Dice upon finishing a long rest, as explained below.
A long rest is a period of extended downtime, at least eight (8) hours long, during which a character sleeps or performs light activity: reading, talking, eating, or standing watch for no more than two (2) hours. If the rest is interrupted by a period of strenuous activity – at least one (1) hour of walking, fighting, casting spells, or similar adventuring activity – the characters must begin the rest again to gain any benefit from it. At the end of a long rest, a character regains all lost hit points. The character also regains spent Hit Dice, up to a number of dice equal to one-half of the character’s total number. For example, if a character has eight Hit Dice, he or she can regain four spent Hit Dice upon finishing a long rest. A character can’t benefit from more than one long rest in a 24-hour period, and a character must have at least one (1) hit point at the start of the rest to gain its benefits.
Just as in the real world, D&D characters spend many hours sleeping, most often as part of a long rest. Most monsters also need to sleep. While a creature sleeps, it is subjected to the unconscious condition. Here are a few rules that expand on that basic fact.
Waking Someone : A creature that is naturally sleeping, as opposed to being in a magically or chemically induced sleep, wakes up if it takes any damage or if someone else uses an action to shake or slap the creature awake. A sudden loud noise, such as yelling, thunder, or a ringing bell also awakens someone that is sleeping naturally. Whispers don"t disturb sleep, unless a sleeper’s passive Wisdom (Perception) score is 20 or higher and the whispers are within 10 feet of the sleeper. Speech at a normal volume awakens a sleeper if the environment is otherwise silent (no wind, birdsong, crickets, street sounds, or the like) and the sleeper has a passive Wisdom (Perception) score of 15 or higher.
Sleeping in Armor : Sleeping in light armor has no adverse effect on the wearer, but sleeping in medium or heavy armor makes it difficult to recover fully during a long rest. When you finish a long rest during which you slept in medium or heavy armor, you regain only one quarter of your spent Hit Dice (minimum of one die). If you have any levels of exhaustion, the rest doesn’t reduce your exhaustion level.
Going Without a Long Rest : A long rest is never mandatory, but going without sleep does have its consequences. If you want to account for the effects of sleep deprivation on characters and creatures, use these rules.
Whenever you end a 24-hour period without finishing a long rest, you must succeed on a DC 10 Constitution saving throw or suffer one level of exhaustion. It becomes harder to fight off exhaustion if you stay awake for multiple days. After the first 24 hours, the DC increases by 5 for each consecutive 24-hour period without a long rest. The DC resets to 10 when you finish a long rest.