Ring of Stamina
Aura: Enchantment (Strong)
This ring appears to be a nondescript precious metal band; often, it is sized for the largest finger of a medium humanoid creature, which may fit it to the smallest finger of a large humanoid creature, or on the thick thumbs of a small humanoid creature.
The wearer feels more rejuvenated and vivacious than usual.
When worn: the wearer need only spend half the time per rest to experience its full effect (5 minute short rest, 4 hour long rest, per default). Additionally, when the wearer uses an effect which has a limited number of uses before a rest of any kind (such as spell slots, bardic inspiration, channel divinity, the lucky feat, etc.): roll a d20; if greater than 10, that usage is not expended.
Clerics in the Life domain can create one of these rings by using a modified variant of Bless at the 5th or higher level which takes 10 minutes to cast on a mundane ring. In addition, deities of the Life domain can create such rings freely, and can be swayed to do so (e.g., via Religion).
The AC and HP are the same as the progenital mundane ring. When broken, its effects merely cease.
Per Detect Magic, the ring has a strong aura of enchantment.
When wearing multiple such rings, the effects do not stack. A worn Ring of Greater Stamina supersedes (and includes) all effects of a Ring of Stamina.
Despite its low rarity (which I am not changing right now), this is easily one of the most broken items in this collection. It expands the expected value of all consumables by a little over 1.5 times--which doesn't sound like much, until you realize that the consumables it covers are things like bardic inspiration, luck dice, portent dice, 9th-level spell slots, tides of chaos, ...
Not knowing this, the creation method is overly simple and easy for something of this power. E.g., in this setting, Amon and Helen can basically create them freely.
If you take this item, you may want to adopt a harsher rarity. (And, for goodness' sake, _never_ give away a Ring of Greater Stamina, or a Greater Anything, for that matter.)