Sounds like a good idea to lay a skeleton first, so you don’t end up spitting a giant in the middle of a city and the NPCs stop being NPCs. Start with the lore lock: figure out what the cryptid actually is, what its myth says, and why it should exist in your world. Then decide the spawn mechanics—do you drop it in a swamp, or let it stalk a specific quest line? Map out its interactions: what loot does it drop, who gets angry, who might actually appreciate a new beast? Write a simple chain: intro scene, reveal, aftermath, and a hook for the next mod. Keep the core rules tight, so you can plug it in and the world still feels consistent. Once the skeleton’s there, you can let the creative chaos bleed in.