Magic Items

Ring, very rare (requires attunement)

While wearing this ring, you regain 1d6 hit points every 10 minutes, provided that you have at least 1 hit point. If you lose a body part, the ring causes the missing part to regrow and return to full functionality after 1d6 + 1 days if you have at least 1 hit point the whole time.

This bag superficially resembles a Bag of Holding but is a feeding orifice for a gigantic extradimensional creature. Turning the bag inside out closes the orifice.
The extradimensional creature attached to the bag can sense whatever is placed inside the bag. Animal of vegetable matter placed wholly in the bag is devoured and lost forever. When part of a living creature is placed in the bag, as hapens when someone reaches inside it, there is a 50 percent chance that the creature is pulled inside the bag. A creature inside the bag can use its action to try to escape with a successful DC 15 Strength check. Another creature can use its action to reach into the bag to pull a creature out, doing so with a successful DC 20 Strength check ( provided it isn't pulled inside the bag first). Any creature that starts its turn inside the bag is devoured its body destroyed.
Inanimate objects can be stored in the bag, which can hold a cubic foot of such material. However, once each day, the bag swallows any objects inside it and spits them out into another plane of existence. The DM determines the time and plane.
If the bag is pierced or torn, it is destroed, and anything contained within it is transported to a random location on the Astral Plane.
Ambledragon said this bag would help cover up mistakes and deal with challenging individuals. I wonder how many "mistakes" he has used it on in the past....
This item can be found in the Dungeon Master's Guide.

Wondrous item, very rare

This book describes fitness exercises, and its words are charged with magic. If you spend 48 hours over a period of 6 days or fewer studying the book's contents and practicing its guidelines, your Strength score increases by 2, as does your maximum for that score. The manual then loses its magic, but regains it in a century.

Prime, Astral, Far Realm, Avernus, Abyss, Elemental Earth

The storm giant quintessent Dessa imbued this belt with her elemental strength. When the belt’s fantastic strength is used lightning dances around the wearer while a warm desert wind blows in the area.

Defender
Weapon (any sword), legendary (requires attunement)
You gain a +3 bonus to attack and damage rolls made with this magic weapon.

The first time you attack with the sword on each of your turns, you can transfer some or all of the sword’s bonus to your Armor Class, instead of using the bonus on any attacks that turn. For example, you could reduce the bonus to your attack and damage rolls to +1 and gain a +2 bonus to AC. The adjusted bonuses remain in effect until the start of your next turn, although you must hold the sword to gain a bonus to AC from it.

Armor (chain mail), legendary (requires attunement)

While wearing this armor, you gain a +3 bonus to AC, you are immune to fire damage, and you can understand and speak Primordial. In addition, you can stand on and walk across molten rock as if it were solid ground.

The efreeti Prince Rashidi al-Zahar ibn Rath transmogrified an efreeti sultana into this delicate suit of crimson chain mail. The wearer of this armor always feels a slight draft, and sometimes finds it hard to stay focused on a task. This item can be found in the Dungeon Master’s Guide.