This plugin has a range of upgrades to enhance your armor pieces or just plain armor on your server
Omni upgrade is an item you can apply to plain armor and make them able to act as an armor piece for any armor set. Meaning if you have 3 pieces of the phantom set and then 1 piece of Omni armor then it will act as a phantom armor piece
Heroic upgrade makes normal plain armor pieces into heroic armor; heroic armor is leather armor which is more powerful than diamond (you can adjust the values in the config.yml)
Armor upgrades are the same as heroic upgrades but instead they armor for each armor set type and can only be applied to the armor set it's from