neobolts
Explorer
That raises an interesting question, though - about creating a range of monster NPC's in advance, calculating their CR's, and then keeping them on the shelf for building NPCs or rival adventuring parties on the fly. You could have cleric stats representing a L1 cleric, L3, L5, L7, L9, and so on. You could do that for all the basic classes and have it ready on the fly. Assuming I'm in 5E for the long haul, it's something for me to consider - a personal "Rogues Gallery" or "Shady Dragon Inn", if you remember some of those 1980's supplements.
Paizo has an NPC Codex for Pathfinder that does this wonderfully. Level 1-20 NPCs for every class, plus commoners. Would LOVE to have this in 5e.