Magic Items

Wondrous item, rare
You can use an action to blow this horn. In response, warrior spirits from the Valhalla appear within 60 feet of you. They use the statistics of a berserker. They return to Valhalla after 1 hour or when they drop to 0 hit points. Once you use the horn, it can't be used again until 7 days have passed.
Four types of horn of Valhalla are known to exist, each made of a different metal. The horn's type determines how many berserkers answer its summons, as well as the requirement for its use.
If you blow the horn without meeting its requirement, the summoned berserkers attack you. If you meet the requirement, they are friendly to you and your companions and follow your commands. This item can be found in the Dungeon Master’s Guide.
This horn was formed from the skull of a white dragon once offered to Aesandoral the Frostlord. It summons frost salamanders (with the statistics of berserkers). It will also carry your voice loudly as you bellow your battle commands.

Armor, rare
You gain a +1 bonus to AC while you wear this armor. You are considered proficient with this armor even if you lack Proficiency with Medium Armor. This item can be found in the Dungeon Master’s Guide.
The surface of this icy armor is cold to the touch, with tendrils of frost decorating the metal. While wearing this, you have a keener understanding of duty and responsibility.
Despite the material it is made of, the temperature around you always remains comfortable, even in the hottest or coldest environments.

Wondrous item, very rare (requires attunement by a wizard)
While you are holding this leather-bound book, you can use it as a spellcasting focus for your wizard spells, and you gain a bonus to spell attack rolls and to the saving throw DCs of your wizard spells. The bonus is determined by the book’s rarity.
You can use this book as a spellbook. In addition, when you use your Arcane Recovery feature, you can increase the number of spell slot levels you regain by 1. This item is found in Tasha’s Cauldron of Everything.
This book holds all of the archfey Ananeira’s research notes about the cosmos. The pages are black, and whatever is written on it shines like stars. On its cover is a raw moonstone crystal that shines when the light hits it. Holding it makes you more aware of your surroundings and place in the universe, and among the stars. It provides a +2 to your Initiative bonus.

Weapon (longsword), very rare (requires attunement)
You can use a bonus action to toss this magic sword into the air and speak the command word. When you do so, the sword begins to hover, flies up to 30 feet, and attacks one creature of your choice within 5 feet of it. The sword uses your attack roll and ability score modifier to damage rolls.
While the sword hovers, you can use a bonus action to cause it to fly up to 30 feet to another spot within 30 feet of you. As part of the same bonus action, you can cause the sword to attack one creature within 5 feet of it.
After the hovering sword attacks for the fourth time, it flies up to 30 feet and tries to return to your hand. If you have no hand free, it falls to the ground at your feet. If the sword has no unobstructed path to you, it moves as close to you as it can and then falls to the ground. It also ceases to hover if you grasp it or move more than 30 feet away from it. This item is found in the Dungeon Master’s Guide.
The blade of this elegantly curved elven longsword is made of the sharpest and coldest ice from the domain of Aesandoral the Ice Lord. As quick as the blizzard winds, it only takes one minute to attune. Its name is inscribed on its blade in Sylvan. Its command phrase is “Long may winter reign.”