NCF – Extended list of Neutral creatures.

Does anyone know how to extract creatures from a megapak? To put it simply, I need a balrog.

Well, to extract a creature from a megapak, you need to understand how mods work. I learned this by tinkering with other people's mods.

But your question is easily solved – just Google "balrog" and find a topic on heroescommunity.
http://heroescommunity.com/filespace/file/NCF%20Balrog.rar
This is a link to the mod, not to the topic, because either the author or some moderator-joker crossed out the correct link to the download and put the link to a VPN below... well, they didn't delete it, thankfully.