Harmony - Troop Symmetry

Can we finally say that the developers have decided what Nightmares are:

Nightmares are unicorns that have changed over time due to the influence of Malassa. Their fur has become as dark as onyx, their muzzles are gaunt and tormented, and their clear eyes are completely black. Their horn, once a symbol of fertility, has become a vessel and physical embodiment of the nightmares that these creatures are cursed to see and feel.
The thunder of Nightmares' hooves creates waves of horror that penetrate and spread through the ranks of enemies. A Nightmare horn obtained in battle is a precious artifact. Processed and fitted with a handle or shaft, it can become a sword or spear that contains and transmits the same nightmares that the creature itself has absorbed.

- or are they the result of Ashi's work (unicorns corrupted by darkness)