In power level 10 requirements there is “Collect a Mythic troop”. Right now the only mythic from Karakoth is Zuul’Goth. Maybe a more affordable mythic from Karakoth will appear sometimes?
In a stream Sirrian or Nimhain mentioned that Karakoth will have a regular Mythic.
You can craft Zuul’Goth, so this is not an impossible mission.
Out of the 90k players that are actively playing GoW (according to Ranked PvP). I know of 2 people crafting Zuul’Goth thus far.
But, the bottom line is, it’s there to be crafted.