Against Shubnigurath, during reckoning, you have to spawn a monster in an random space. What happens if the monster has a 'when spawned, move to area so and so"?
Where does the monster appear?
Spawning in a random space a "When Spawned" monster?
The monster spawns on a random space. Then if that monster has any "When this Monster is spawned" effects you resolve those effects.
So, in your example, it would spawn on a random space and then move to area so and so.