I have completed the invasion in excess of 20 times on the moon, killing all 3 of the gatelords and the overlord never spawns. I have tried killing hydras, not killing hydras, nuking the boss within seconds, I even stayed in one instance to do the whole thing 4 times in a row earlier and still the boss won't spawn. Can you confirm the conditions that make the overlord spawn, time is running out for the title and it is the one thing that is holding me back.