Oblivion Fragment忘却のかけら

A piece of obliterated antimatter. It has a deep connection to entities living in negative space and plays a key role in attracting one.
In-game description

How to use Oblivion Fragment

Oblivion Fragment is used to craft Wind Organ of Void. You do not need a crafting station: you use Oblivion Fragment itself.

Have the materials in your inventory.
Put Oblivion Fragment in your hotbar, select it and use it (right-click).
Wind Organ of Void is crafted.

Oblivion Fragment key points (from the game data)

Best source: Void Caveling Brute — 65.3% chance per kill.
Sells to merchants for 20 Ancient Coins.

Calculated and summarized by this site from the game data (1.3.0.6).

What is Oblivion Fragment used to make? Craftable items and their uses

Items you can make with Oblivion Fragment, with how to craft them, the other materials needed and what the result is for.

Wind Organ of Void

How to craft: Hold Oblivion Fragment and use it (no crafting station needed)
Materials: Oblivion Fragment ×10
What it is: Placeables & furniture. "A ritual instrument that works with wind blowing through its cavities. The sound it plays is perfectly tuned to attract a beast of oblivion."

How to get Oblivion Fragment (Enemy drop)

Enemy drop (5)

Source	Type	Biome	Amount	Chance
Void Caveling Brute	Enemy drop	Breaker's Reach	1–2	65.3%
Void Caveling Shaman	Enemy drop	Breaker's Reach	1–2	65.3%
Void Caveling	Enemy drop	Breaker's Reach	1–2	65.3%
Void Larva Cocoon	Enemy drop	Breaker's Reach	1	21.4%
Void Larva	Enemy drop	Breaker's Reach	1	9.9%

"Chance" is the chance to get at least one of this item per try (opening one chest, defeating one enemy, one catch). A "guaranteed group" is the group of a chest or boss from which exactly one item always drops; it does not mean this item always drops (the chance of it being picked from that group is shown in small text). Only items that always drop are marked "Guaranteed". Fishing means catches with a fishing rod, separate from enemy and boss drops. Calculated from the game's drop tables (Conf/Loot, 1.3.0.6) the same way the game rolls them.

What Oblivion Fragment is used for (1 recipe)

	Recipe (materials)
Wind Organ of Void	Oblivion Fragment×10	106