Pillar of Nirn is a medium armor set. When you deal damage, you have a 10% chance to create a fissure underneath the enemy after 1 second, dealing 2000 Physical Damage to all enemies within 2.5 meters and causing them to bleed for an additional 8000 Physical Damage over 10 seconds. This effect can occur once every 10 seconds.
This set procs very easily when you have a damage over time effect on the enemy. Once it procs it deals a bit of physical damage and applies a big bleed on the enemy that lasts for 10 seconds.
The Pillar of Nirn set is part of the Horns of the Reach DLS. It drops in Falkreath Hold in Craglorn. Each set item is bound on pickup. You can acquire medium armor, weapons and jewelry of this set in the Dreadhorn motif style.