Wormwood: D.U.M.B.s (Deep Underground Military Bases) - Book 5 - D.U.M.B.s (Deep Underground Military Bases)

The prophecies call the returning planet "Wormwood" and it's making an orbit near Earth after thousands of years, trailing asteroids that will cause mass destruction. A secret military group prepares to launch a counterstrike to avert the catastrophe in space before it reaches Earth. Meanwhile, an ancient alien threat comes back to life deep below the Earth's surface, deeper than even the deepest D.
U. M. B.s. This is Book 5 in the continuing series, so be sure to start with Book 1: Greyland. This running series is 7 books, all parts are now out. The series is complete. A stand-alone prequel story is mostly written, so check back for that in summer (or later) 2021.