Vorpal Shards

If you happen to fall over a Vorpal Shard, well, then you're in luck, as these give a substantial upgrade to the performance of your weapon. These can be found in Advanced or higher raid caches
The way they work is by adding a flat +5% to Damage, Recoil, Spread, and Reload speed. 
A single weapon can be sharded 5 times, the first star costs 1 Vorpal Shard, while the next costs 2 etc. 
Once a Weapon has hit 3 stars, it can only be upgraded further with Xen Shards, the same above applies!

Xen Shards

These Strange shards are the result of combing the rare material Resin and  Vorpal Shards
Forming a dark green Shard that glows with an otherworldly power know as  Xen shards
They work the same as Vorpal Shards by adding a flat +5% to Damage, Recoil, Spread, and Reload speed. 
With Xen Shards being the last items needed to obtain a  5 shard Item.

Void Shards

Beginning from Uncommon Hellish, you have the ability to stumble across a fractured piece of the void. 
These Void Shards appeared after the Loot Goblins got ahold of a supply of Void Stones. Kill those bastards and complete 
qualifying to have a chance to obtain these shards. Combining 8 of these shards will grant you a Void Stone. You can use this stone on 
Abyssal weapons/gear to upgrade it to the final tier.  Void Stones can be found starting at Epic Hellish. After further research into the origins of these stones, its 
been determined that completing a Hellish raid of -REDACTED- difficulty will grant the owner of the key a Void Shard, and increased chances to those who lived to the end!