These items, bought on the in-game store for 1,500 Caliber (premium currency), vastly increase your chosen weapon or Descendant’s mod capacity.
The comparison to Warframe is not a complimentary one, especially given how similar the bones of The First Descendant is to Digital Extremes’ own sci-fi shooter.
The First Descendant is out, and making waves on both PC and consoles.
The more mod capacity you have, the more powerful mods you can equip, which in turn allows you to take on harder content.