Magic Items

Heavy armor, legendary

You have a +3 bonus to AC while wearing this armor. Source: DMG.
This plate armor was recovered from the ursine archons that guard the gate to Mount Celestia. It still smells of bear.
Guardian. The item whispers warnings to its bearer, granting a +2 bonus to initiative if the bearer isn't incapacitated.

Wondrous item, legendary (requires attunement by a spellcaster)

This wondrous item can be a scepter, an orb, an amulet, a crystal, or another finely crafted object. It typically incorporates imagery of dragons' wings, claws, teeth, or scales.

Due to the strange magic that trapped Amaranthraxine’s spirit in the walls of Xorvintroth, this hoard item can’t increase or decrease in power.

You have advantage on initiative rolls. While you are holding the focus, it can function as a spellcasting focus for all your spells.

Gem. Whenever you use a spell slot to cast a spell, you can immediately teleport to an unoccupied space you can see within 15 feet of you.

While you are holding an Ascendant focus, you can use it to cast certain spells. Once the item is used to cast a given spell, it can't be used to cast that spell again until the next dawn. The spells are determined by the family of the dragon in whose hoard it became Ascendant. An asterisk indicates a new spell that appears in this book.

Gem. Rary's telepathic bond, Raulothim's psychic lance

In addition, when you cast a spell of 1st level or higher while holding this focus, you can treat the spell as if it were cast using a 9th-level spell slot. Once this property is used, it can't be used again until the next dawn.

Wondrous item (tattoo), legendary (requires attunement)

Produced by a special needle, this magic tattoo evokes fury in its form and colors.

Tattoo Attunement. To attune to this item, you hold the needle to your skin where you want the tattoo to appear, pressing the needle there throughout the attunement process. When the attunement is complete, the needle turns into the ink that becomes the tattoo, which appears on the skin.

If your attunement to the tattoo ends, the tattoo vanishes, and the needle reappears in your space.

Bloodthirsty Strikes. The tattoo has 10 charges, and it regains all expended charges daily at dawn. While this tattoo is on your skin, you gain the following benefits:

When you hit a creature with a weapon attack, you can expend a charge to deal an extra 4d6 necrotic damage to the target, and you regain a number of hit points equal to the necrotic damage dealt.
When a creature you can see damages you, you can expend a charge and use your reaction to make a melee attack against that creature, with advantage on your attack roll.

Weapon (warhammer), legendary (requires attunement by a dwarf)

Whelm is a powerful warhammer forged by dwarves and lost in the dungeon of White Plume Mountain.

You gain a +3 bonus to attack and damage rolls made with this magic weapon. At dawn the day after you first make an attack roll with Whelm, you develop a fear of being outdoors that persists as long as you remain attuned to the weapon. This causes you to have disadvantage on attack rolls, saving throws, and ability checks while you can see the daytime sky.

Thrown Weapon
Whelm has the thrown property, with a normal range of 20 feet and a long range of 60 feet. When you hit with a ranged weapon attack using it, the target takes an extra 1d8 bludgeoning damage, or an extra 2d8 bludgeoning damage if the target is a giant. Each time you throw the weapon, it flies back to your hand after the attack. If you don’t have a hand free, the weapon lands at your feet.

Shock Wave
You can use an action to strike the ground with Whelm and send a shock wave out from the point of impact. Each creature of your choice on the ground within 60 feet of that point must succeed on a DC 15 Constitution saving throw or become stunned for 1 minute. A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success. Once used, this property can’t be used again until the next dawn.

Supernatural Awareness
While you are holding the weapon, it alerts you to the location of any secret or concealed doors within 30 feet of you. In addition, you can use an action to cast detect evil and good or locate object from the weapon. Once you cast either spell, you can’t cast it from the weapon again until the next dawn.

Sentience
Whelm is a sentient lawful neutral weapon with an Intelligence of 15, a Wisdom of 12, and a Charisma of 15. It has hearing and darkvision out to a range of 120 feet.

The weapon communicates telepathically with its wielder and can speak, read, and understand Dwarvish, Giant, and Goblin. It shouts battle cries in Dwarvish when used in combat.

Personality
Whelm’s purpose is to slaughter giants and goblinoids. It also seeks to protect dwarves against all enemies. Conflict arises if the wielder fails to destroy goblins and giants or to protect dwarves.

Whelm has ties to the dwarf clan that created it, variously called the Dankil or the Mightyhammer clan. It longs to be returned to that clan. It would do anything to protect those dwarves from harm.

The hammer also carries a secret shame. Centuries ago, a dwarf named Ctenmiir wielded it valiantly for a time. But Ctenmiir was turned into a vampire. His will was strong enough that he bent Whelm to his evil purposes, even killing members of his own clan.

Proficiency with a warhammer allows you to add your proficiency bonus to the attack roll for any attack you make with it.

Dungeon Master's Guide , pg. 218