Material lists for tiers don't work. Using the default tier.yml formatting, but with Materials, the code won't read the Material lists.

Legendary:
  Color: Gold
  Chance: 3
  Material:
  - Diamond_Sword
  - Diamond_Axe
  Enchantments:
    Amt: 7
    Levels: 10
  Lore:
  - 'Required Level: 500'

This tier.yml results in all kinds of items, not just diamond swords and diamond axes. The best possible thing to do, I think, is to switch from using material names to using material ids.

I might need to refine the wiki a bit..

Legendary:
  Color: Gold
  Chance: 3
  Materials:
  - 'Diamond_Sword'
  - 'Diamond_Axe'
  Enchantments:
    Amt: 7
    Levels: 10
  Lore:
  - 'Required Level: 500'

Materials was the problem. However the photo shows autoloading prefix suffix.