Runes/Sigils
They are probably classed as crafting materials because Runes of Holding are used to craft bags/boxes for inventory.
[Zeus] Guild ~ Desolation. Not some silly muffin thing, stop stalking me Dhiania!
Well, in that case have items filtered by the tag that’s in the description. I dont need all these runes and sigils in my bag because 1 out of a million is a crafting material. If they can make an exception for the ecto’s, they can make an exception for the rune of holding.