We’ve been grinding for this overlord for two days and haven’t had it spawn. We’ve tried all the different theories I’ve found online, is there actually a specific way to get it to spawn or is it pure randomness?
Is this for the Wandering Nightmares triumph? If this is in reference to the Vex Incursion, then wait until there is a public event in the Hellmouth. Once the public event has completed, a few minutes afterwards the Vex Incursion will begin and three waves will spawn. Each of the waves will have a boss Vex Overlord that can be killed.