Magic Items

Two walrus tusks that are trapped (see below), one of which is an ivory-covered bronze horn of Valhalla.
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. The GM chooses the horn's type or determines it randomly.
d100 Horn Type Berserkers Summoned Requirement
01-40 Silver 2d4 + 2 None
41-75 Brass 3d4 + 3 Proficiency with all simple Weapons
76-90 Bronze 4d4 + 4 Proficiency with all Medium Armor
91-00 Iron 5d4 + 5 Proficiency with all martial Weapons
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.

Weapon (any), uncommon (+1), rare (+2), or very rare (+3)
You have a bonus to attack and damage rolls made with this magic weapon. The bonus is determined by the weapon’s rarity.

Ring, uncommon (requires attunement)
While wearing this ring, you are immune to magic that allows other creatures to read your thoughts, determine whether you are lying, know your alignment, or know your creature type. Creatures can telepathically communicate with you only if you allow it.

You can use an action to cause the ring to become invisible until you use another action to make it visible, until you remove the ring, or until you die.

If you die while wearing the ring, your soul enters it, unless it already houses a soul. You can remain in the ring or depart for the afterlife. As long as your soul is in the ring, you can telepathically communicate with any creature wearing it. A wearer can’t prevent this telepathic communication.

Wondrous Item, uncommon This serpentine statuette of an owl can become a giant owl for up to 8 hours. Once it has been used, it can't be used again until 2 days have passed. The owl can telepathically communicate with you at any range if you and it are on the same plane of existence. This item is found on Magic Item Table G in the Dungeon Master’s Guide.

A small iron casket among the oni’s belongings holds a gift to the Lord of Oni—a trick box made out of eighteen plates of platinum, eighteen plates of electrum, and eighteen plates of silver. The box is opened by sliding certain plates on the left side, then the top, then the right side in a particular sequence. The correct order is platinum–electrum–silver on each end, and silver–electrum–platinum on the top.
The box has properties similar to those of a bag of holding—although the container is but 10 inches long by 6 inches wide and 4 inches deep, it holds 3 cubic feet of material or 60 pounds, whichever is the lesser.

Weapon (javelin), uncommon
This javelin is a magic weapon. When you hurl it and speak its command word, it transforms into a bolt of lightning, forming a line 5 feet wide that extends out from you to a target within 120 feet. Each creature in the line excluding you and the target must make a DC 13 Dexterity saving throw, taking 4d6 lightning damage on a failed save, and half as much damage on a successful one. The lightning bolt turns back into a javelin when it reaches the target. Make a ranged weapon attack against the target. On a hit, the target takes damage from the javelin plus 4d6 lightning damage.

The javelin’s property can’t be used again until the next dawn. In the meantime, the javelin can still be used as a magic weapon.