I have Athena at level 10. She has under 14 morale. When I choose monsters to support her in attacking enemy islands, I recently choose the phoenix as one of the monsters. Because I don’t have 14 morale, the blue bar would fill up and then monsters would not be spawned - not even the ones with less than 14 morale.
It would be great if the game identified that you had selected a monster that you were unable to spawn. Your morale is not shown anywhere in the info stats so until you start the attack (or you make notes about your hero’s starting morale) you don’t know your starting morale. Choosing a monster you are unable to spawn (because you don’t have enough morale), wastes a slot and usually loses you the attack.