Offered for pre-order on SourceHorsemen.com starting in June 2016, the Covenant of Shadows wave added 8 new figures into the Realm of Mythoss, including the popular Templar Legion Builder and the lines second deluxe accessory-filled builder set, the Knight Builder.
This wave was also the first one to have an overarching storyline presented as part of the release:
"Long ago, when endless night finally surrendered to light of day, the followers of the ancient evils broke into four different factions, each dedicated to their masters’ return. Gathering in the secret corners and forgotten fringes, these groups grew in size and silently summoned fervent multitudes to their disparate and isolated armies. Now that the armies have been amassed they are fueled by their faith in their masters’ imminent arrival. In anticipation of that arrival, the faction leaders all sent their most trusted emissaries to a secret meeting where a horrible pact was born - The Covenant of Shadow."