A rune pouch is great whenever you have one or two spells you are using as your main spells. For example, if you are using ice spells a lot for offense, you will need a lot of water, blood, chaos, and death runes. You can store the water and death runes, which are used for all of the four ice spells into the rune pouch and have a ton of them. Then, depending on if you are using ice blitz and ice barrage as your main spells, you can store blood runes. If you are using ice rush and ice burst, you can store chaos runes. No matter what you do, you can easily store the other rune inside your inventory to have access to all four spells. However, the rune pouch's use does save space as you only need to pack your inventory with one rune instead of 4.