I think you might be detecting a theme here with the dragons.
Here is the cover of Book 5, Darkness.
I’m not sure if you guys remember the details of the book, but it was the black sheep of the series, in my opinion. Most of it took place underground in Bunker 132, and was mainly Alex and the crew dealing with the weird cult.
It was a bit hard to convey that on a cover in a way that matched with the rest, so instead this one shows some dragons in the mountains, since at the end of Darkness, there does happen to be a battle with dragons in the mountains.
Either way, it looks awesome and I’m happy at how it turned out.
Just two covers left before the entire series is complete!