NCF – Extended list of Neutral creatures.

""""AstralLeinBy the way, I once created a King Wyvern creature. It had the ability to consume corpses. Because of this, the game crashed at the beginning of each turn. The reason was simple: I assigned this ability to the King in the spells, but I didn't specify it among the creature's abilities, and the game couldn't identify it. I added it to both, and the crashes stopped."""""

Wyvern is a mythical creature, a type of dragon with one pair of legs, often depicted with a snake-like tail, sometimes with a venomous stinger....
King Wyvern is a more powerful version of the wyvern...

indeed, the mod is missing a file
MapObjects\_(AdvMapObjectLink)\Monsters\NCF\Creature_389.xdb

take it from the megapack

I don't want to search for creatures, if you want to, you can do it yourself - here's a link to the list of creatures from that forum http://heroescommunity.com/viewthread.php3?TID=27275
but so much time has passed that many images have stopped displaying, and the links are dead... it's sad, I really loved browsing this forum back in 2013.