Collect an Essence of a Chosen.

Although you only need one for this achievement, you must defeat all five of the Chosen as you need their materials to upgrade 5 Enhancements to Balanced. You can buy an additional one through Vulgrim for 5,000 souls after the second Wrath fight. It'll be under BUY>INGREDIENTS. Their locations are:

The Flame Warden (Serpent Hole, Hollows - Antechamber)
Templar of the Damned (Serpent Hole, The Depths, Forgotten Lake)
Agony (Sperpent Hole, Haven - West End) Requires Stasis Hollow and Force Hollow
Corrupted Tomekeeper (Serpent Hole, Bonelands - Cargo Hold)
The Grock (Serpent Hole, Scar - Chasm Overlook) For this Chosen, the story leads you to him to progress forward.