[Shadow] Item - Horn of Resounding Echoes

Ancient Aziran dwarves used horns like these when charting the cavern systems around their subterranean homes. After the Blight forced society and other monsters underground, they have become more of an attention-grabbing hazard. Nowadays, they're used mainly for dwarven ceremonies.

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Horn of Resounding Echoes
Wondrous item, uncommon

You must use an action to blow into the horn. When you do, it produces a reverberant sound heard up to 120 feet away whose echoes linger five times as long. 

Thunderburst. Whenever you blow into the horn, you can choose to roll a d20. On a roll of 18 or higher, you produce the effects of a thunderwave spell (save DC 13).

Resonant Echo. You can use an action to blow into this horn, producing a powerful blast of sound that can be heard up to 300 feet away. Unless you are deafened, the echoes allow you to learn the basic details of the environment within 60 feet of you: the general layout—typically walls, ceilings, and objects—as well as the location of creatures that are not Hidden from you. You glean nothing from areas that are magically silenced or areas protected against sound. What you learn is limited to the moment you blow the horn, and does not provide you with detailed information such as the number of creatures in a horde, or information about motion, such as the direction a creature is headed. Once you use this property, you can't use it again until after 1d3 dusks. 

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Rare Variant. The rare version of this horn has these changes. The Thunderburst property produces the effects of the thunderwave spell cast at 3rd-level instead of 1st-level (save DC 15 instead of 13). Additionally, the range of the Resonant Echo property is 90 feet instead of 60 feet. 

Very Rare Variant. The very rare version of this horn has these changes. The Thunderburst property produces the effects of the thunderwave spell cast at 5th-level instead of 1st-level (save DC 17 instead of 13). Additionally, the range of the Resonant Echo property is 120 feet instead of 60 feet.

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DESIGN COMMENTARY

I designed this item as a product of cavern exploration — as a way for past NPCs to assist in mapping out dangerous dark caves. The idea was (sorta like echolocation) to use echoes to accomplish this, kind of like a brief Daredevil vision. This property is a very strong one; it originally functioned like blindsight, but I later remedied it to be a little stronger allowing for seeing behind corners.

I used a couple ways to balance this property. As a basis, it doesn't require attunement because it's already a limited item that doesn't provide much consistent benefit. To remedy this, I extended the recharge duration to 1d3 days, and ensured that when using the property, it will always alert nearby stealthy or hidden creatures. As an item, its best use is mapping the layout of a maze; it has minor use as a way to detect invisible creatures, but you'd have to follow up with an ally capable of casting faerie fire before the invisible enemy moves.

To keep the horn from being a one-trick pony, I added the Thunderburst property. It's mostly for flavor since it's unlikely you'd have it work as intended in combat.

Visually, I experimented with a couple ideas. I went all-in on the dwarven design though it's not that visible :(, and I liked how the wings improved the silhouette even though it doesn't really make sense. The wings could be bat wings or dragon wings, both of which have blindsight. I even added a  small dwarven pattern on the wings, but it looked a little too much like ribbed metal flooring so I turned that down a bit. Overall not my favorite, but respectable.