The Four Rarities

Let's first review the default usage for the four rarities in the game and how these already start to tell a story about your universe. Common elements are prevalent enough, at least among adventurers, that a player is assumed to be able to access them provided they meet the prerequisites (if any). Uncommon elements are difficult to access or regionally specific, but a PC can usually find them eventually with enough effort, potentially by choosing a specific character option or spending substantial downtime tracking them down. Rare elements are lost technology, ancient magic, cutting edge biotech, and other options that PCs can access only if you specifically make them available. Unique elements are one of a kind, like a specific magical artifact, one-of-a-kind prototype, or a named creature. You have full control over whether PCs can access them. Named NPCs are unique creatures, though that doesn't mean their base creature type is unique. For instance, a shirren named Zazi is unique, but that doesn't mean it would be any harder for a PC encountering her to tell she's a shirren—just to discern specific information about her.