When I was building my Tzaangor, the Mutalith kit was out of stock at GW, so I made my own out of an old Ghorgon kit from AOS that I had laying in the bits box. Basically, I wanted him to be a big Tzaangor! Let's take a look at him!
The conversion is actually pretty simple and requires only a few bits, some basic green stuff work, a drill and some sculpting tools.
So if you take a close look at the model, there are a ton of eyes and tentacles on the shoulders and back. They are all from the Chaos Spawn kit. A 1/8 Drill bit will make holes that these bits will fit perfectly into with no green stuff. Next, you want to add a beak. Just add a little green stuff and shape it out off of the original mouth and smooth it out. It will work out fine. I did flames in the hands because those are the hands I had and the best idea I had at the time. You could make it with horrors in its hands, a giant weapon. It's all good.
I also added the Chaos symbol from the Chaos Warshrine and made the portal with green stuff and a transdimensional beamer bit from the Necron Night Scythe bit, but you could sculpt your own.
Overall, I like the final look of the model and it could also be paired with my beastmen as a Cygor to run with my Tzaangor!
Let me know what you think or show me some pics if you have a crazy Mutalith or a cool converted Cygor or Ghorgon.