Depending on how far back in time we really are, we might have found how the Red Dragons were able to resist the Cosmic Dracorage shit the Void/Others pulled back when their first push brought down the Empire of the Dawn. The Dragons could have gotten a mysterious boost to their Will saves courtesy of an unknown benefactor acting through the Dragon Dream...
Perhaps even a Planes-wide shot of Mythic Dragon juice brought to them by their friendly neighborhood descendant, Viserys Targaryen, appearing in Red Dragon form to them all simultaneously via the Dragon Dream so they could benefit from his Beacon of Will feat at just the right time.
(Mythic) Beacon of Will: All allied beings who can see, hear or somehow physically perceive you and who accept your rule and aid gain the benefits of
Indomitable Soul against non-Mythic effects. For instance, being present on a battlefield affects the whole army, however being in telepathic communion with someone from whom you are otherwise separated from does not confer the bonus.
And thus Viserys steps into Legend (again)...