A poisoned creature has disadvantage on attack rolls and ability checks.
When a poisoned creature takes poison damage equal to or greater than its Constitution modifier (minimum of one), its Stamina maximum is reduced by 1d6.
While poisoned, if a creature’s Stamina maximum is reduced below half its normal value, then the creature suffers one level of exhaustion that cannot be removed. This exhaustion persists even if the creature is no longer poisoned, as long as its Stamina maximum is reduced below half.
A creature’s Stamina maximum recovers at the end of a long rest, as long as it is no longer poisoned during the rest. Healing using recovery dice or magical means also restores the same amount of the creature’s Stamina maximum, provided that the creature is no longer poisoned.