When the Adeptus Mechanicus invokes an ancient pact with the Dark Angels, Ezekiel, Grand Master of the Librarians, must lead the 5th Company to liberate the planet of Honoria from a vast ork army. Even reinforced by the regiments of the Astra Militarum, the Dark Angels face a tremendous challenge, and the Adeptus Mechanicus appear to have their own reasons for becoming involved in this conflict…

Read it because

It's a tale of one of the more mysterious of the Dark Angels heroes (and that's saying something for that Chapter), bringing the former First Legion into conflict with enemy and ally alike.