NCF – Extended list of Neutral creatures.

Is it certain that the ABILITY_BLADE_BARRIER was created by the developers and hasn't been modified by players? None of the standard creatures have it, and it's not listed anywhere. Also, it seems too powerful compared to other abilities.

Well, it makes sense that it was created by the developers. All abilities are coded in the executable file, which means they can't be deleted, added, modified, or rebalanced. The last one might be possible if the developers accounted for it...(I don't remember where, but there seems to be a file that contains parameters for some abilities).