On some of the Darkness cards, in the Event step of the card, it can direct you to spawn something eg a captain.
I can't see in the rules what to do in this situation if there is no lair. I know you ignore the Spawn step if there is no lair but do you ignore all other spawn commands (unless it stipulates somewhere else for it to spawn)?
If not lair, no spawn, ignore all spawns.
But if the text says: "appear", summon the captain.