Heroes 5.5 WarGame Edition - Tactical Edition.

Once you draw a Viseryon for 5 heroes, then we can think about strengthening the Necrodrakes; I was guided not only by the general logic of undead but also by visuals. They don't look equal to Black Dragons in my opinion.
They lack dragon fire/acid, they lack dragon mass, and even their wings are tattered. All that remains of a dragon is fear. It is with fear/debuffs that they kill. Despite individual weakness, this is a very serious and key unit (the dragons of Fate are especially dangerous – it’s no coincidence they have such a name; it’s hard to kill them under Etherealness, and the debuffs work incredibly well; if most of the enemy army is bitten by them = the battle is lost).