Iron Vrykul are a variant of vrykul composed of iron. Like the iron dwarves and iron giants, they are servants of Loken.
The names of some trash mobs hint that some of them are made of hardened steel and titanium, but it seems they are still part of the 'armies of iron'.
The only apparent creator of iron vrykul is a fire giant named Volkhan, who can be seen forging new additions to the iron vrykul army in the Halls of Lightning. Iron vrykul are stored below Forge of Wills, and may be made there, but are not shown being made there. In the end however, it is clear that no matter what the process used to create them, Volkhan is ultimately the "factory worker" building them, while Loken himself is "the boss" that owns them.
World of Warcraft: The Magazine Issue 5 says that the titans created the vrykul, and that the
vrykul turned into humans due to the Curse of Flesh, with no other stages mentioned. The iron races are grouped separately.