Conditions alter a creature’s capabilities in a variety of ways and can arise as a result of a spell, a class feature, a monster’s attack, or other effect. Most conditions, such as blinded, are impairments, but a few, such as invisible, can be advantageous.
A condition lasts either until it is countered (the prone condition is countered by standing up, for example) or for a duration specified by the effect that imposed the condition.
If multiple effects impose the same condition on a creature, each instance of the condition has its own duration, but the condition’s effects don’t get worse. A creature either has a condition or doesn’t.
The following definitions specify what happens to a creature while it is subjected to a condition.
Exhaustion [table pg 358]
If an already exhausted creature suffers another effect that causes exhaustion, its current level of exhaustion increases by the amount specified in the effect’s description.
A creature suffers the effect of its current level of exhaustion as well as all lower levels. For example, a creature suffering level 2 exhaustion has its speed halved and has disadvantage on ability checks.
An effect that removes exhaustion reduces its level as specified in the effect’s description, with all exhaustion effects ending if a creature’s exhaustion level is reduced below 1.
Finishing a long rest reduces a creature’s exhaustion level by 1, provided that the creature has also ingested some food and drink. Also, being raised from the dead reduces a creature’s exhaustion level by 1.