Necklace of the Nap (5e Equipment)
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Wondrous item, common (requires attunement)
For a long rest you only need 4 hours and a short rest can be taken in 30 minutes.
However, you still need to get at least 6 hours of sleep a day, unless your race says otherwise.
You can divide the 6 hours into smaller naps. The sum of naps slept must correspond to 6 hours of sleep.