Make your way to the furnace tower in the area. The Nornir Chest is next to the crane. Light, the C Rune, left to the chest and then head right. Jump across and destroy the barrels on the left for the R Rune. Turn around and enter the opening. The N Rune will be behind an iro...
Each Nornir Chest gives you 1 Apple of Idunn (Health Upgrade) or Horn of Blood Mead (Rage Upgrade). This makes them one of the most useful collectibles in the game because they increase your two main stats. Especially on higher difficulties you should get all of them as early as possible...