Balorgh is a Monster Set (Helm and Shoulder) available in light, medium or heavy armor. It drops in the Balorgh (unique) style.
The 1-piece set bonus adds 129 Weapon Damage and 129 Spell Damage.
2-piece set bonus: When you use an Ultimate ability, you gain Weapon and Spell Damage for 10 seconds equal to twice the amount of total Ultimate consumed.
For example, this means if you save up 500 Ultimate points, you will gain 1000 Spell and Weapon Damage for 10 seconds.
The Shoulder can be acquired by using an Undaunted key on Urgalag Chief-Bane's chest. The Shoulder type, weight and trait are RNG based and can be from any dungeon this NPC gives Pledges for.
The Helm can be acquired from March of Sacrifices which is part of the Wolf Hunter DLC and located in Greenshade. The Helm is guaranteed to drop from the final boss in veteran mode only. The weight and trait are RNG based.
You can mix-and-match Monster Set shoulders and helms from different sets and add two 1-piece bonuses to your build, or wear a complete set to take advantage of the full 2-piece set bonus.