Loimos was preparing for lengthy invasions, lengthy occupations of living lands, to take upon places where death might normally struggle to reach, to this end, the pure undead taught his soldiers how to be feared, and how to be beloved by the living populations, how to be alongside them, which was why his rank and files, and main knights were entirely veiled, hiding their undeath, trained in building their own camps and fortifications, smiths and various other non-combat professions were taught to them in simple amounts, alongside the presence of actual experts.
Their leader, Loimos could do all of this with his rot in the blink of an eye, but his forces were meant to be capable of operating on their own, the culling of the islands all around Viridis was set to impart all of those ideas, the forces present with him here, still of a small amount, would pass on this rich experience upon those that would join them later on.