I read the "spawned" question as "where is it normally found", personally. Like, a sort of tie-in to "monster settings".
So, even if an imp was literally spawned on some other plane, you'd typically find it in a civilized place (hanging out in a wizard's castle) and it wouldn't be too much of a threat.
Or, maybe your imps are more rare, and only found with more powerful wizards, guarding his magic circle or other "places of power", and it would be more dangerous.
So, I like the question in that regard. Maybe it should be "normally encountered" instead of "spawned", if that's the intent.