The Horn of Heimdall, also known as Gjallarhorn, is a mythological instrument of the Norse god Heimdall, the deity who guards Asgard. When Heimdall blows the horn, the blast can be heard throughout the multiverse, and prophecy foretells that Heimdall will sound the horn to gather the gods during Ragnarok. Heimdall also uses the horn as a drinking vessel to imbibe from the well of Mimir, granting him the wisdom that has seeped from the roots of Yggdrasil.

The bronze horn is adorned with Norse runes that foretell the general events of Ragnarok leading up to Heimdall's death. Liquid poured into the bell of the horn magically does not leak from its mouthpiece, allowing it to be used as a drinking vessel. The horn can also magically change in size to better conform to the grip of its user, and it holds up to 4 pints of liquid when sized for a Medium creature.

The horn rarely leaves the possession of Heimdall, who remains ever vigilant in his duty to protect Asgard from intruders. Occasionally, he will drop the horn onto the Material Plane for those he deems worthy. However, once Ragnarok begins, the horn will inevitably return to its master to fulfill its prophecy.

Random Properties. The Horn of Heimdall has the following randomly determined properties:

• 2 minor beneficial properties
• 1 major beneficial properties
• 1 minor detrimental property

Increased Wisdom. Your Wisdom score increases by 2, to a maximum of 24, while attuned to the horn.

Divine Aid. You can use an action to blow the horn to call your deity to intervene on your behalf.

Describe the assistance you seek, and roll percentile dice. If you roll a number equal to or lower than 20, your deity intervenes. The DM chooses the nature of the intervention; the effect of any cleric spell or cleric domain spell would be appropriate. If your deity intervenes, you can't use this property again for 7 days. Otherwise, you can't use it again until the next dawn.

Summon Bifrost. Whenever you are not underground or indoors, you can use an action to blow the horn. In response, you summon the Bifrost, a burning rainbow bridge of shimmering light that reaches into the heavens, which originates at a point you choose within 120 feet of you. The rainbow is 30 feet wide, 1 foot thick, and stretches further than the eye can see. The rainbow feels harmless despite its appearance, but it forms a solid surface to any creature that comes into contact with it; objects pass through it unaffected.

Traveling along the rainbow at a normal pace for 24 hours leads you to a general location in Asgard, the realm of the Norse deities, which you choose as you blow the horn. If you summon the Bifrost without choosing a location in Asgard, the rainbow's destination defaults to the home of Heimdall, the Norse deity who guards Asgard from intruders. If you attempt to summon the Bifrost from Asgard, you must choose a location on a different plane of existence for the rainbow's destination, at the DM's discretion, otherwise your attempt fails.

The Bifrost lasts until you end your attunement, until it is blocked by a solid surface such as a wall of force, until you blow the horn again, or until the horn is destroyed. Creatures and their possessions on the rainbow as it gets destroyed fall to its plane of origin.

Once you have used this property, it can’t be used again until the next dawn.

Destroying the Horn. The Horn of Heimdall will instantly return to Heimdall's possession when it is used in a continual flame spell for 1 week or destroyed by a disintegrate spell. The only way to permanently destroy the horn is during Ragnarok, when it will crumble to dust as Heimdall is slain by Loki.

Notes: Bonus: Wisdom Score, Bonus: Ability Score Maximum, creature that worships a Norse god, Buff, Utility, Instrument