The Ice Dragon, according to my esteemed comrade Nargott from WGE!
I highly doubt that this comrade has anything to do with the mod.
The original mod for these dragons was released back in 2010 and was called IceDragons; I can share it if needed. The essence of the mod was to recolor the Greydragon's texture into blue tones. The creature's description was also changed, and it was moved to the alternate Greydragon position. However, it lacked effects and had some problems with animations, such as death and attack.
Unfortunately, the author of the mod is unknown because, in those distant years, the mod was published without attribution on one of the fan sites, which no longer exists. I couldn't find it on other resources back then, nor can I now.
When developing the "UNIT" mod in 2014, I borrowed the creature's description and its texture from that mod. I slightly refined the texture and created various effects for the creature, such as icy vapors, breath, death, etc., and also fixed some minor flaws.
It ended up in Phoenix Vision because this mod is based on the visual part of UNIT, and almost all the visual changes were transferred there.
Who to contact regarding copyright is more of a rhetorical question. Since it is unlikely that it will be possible to find the author of the original idea.
[Модификация]Phoenix Vision - Комплексное модифицирование визуального аспекта игры.
[Модификация]UNIT-Баланс существ + визуальные изменения.
[Модификация]NewTransformUndead-Таблица поднятия нежити.
[Модификация]VisualFix-Устрание визуальных багов.
Карты для Heroes V 3.1:
[Карта][1x1]The Last Stand - Дуэльная карта финальных битв
Группа VK:
https://vk.com/club176978884