Actually, he's here. Here are pictures to prove it.
This is a standard plastic Daemon prince with a couple small conversions. I liked the left hand, but thought it looked like it should be holding something. I created the fireball out of a large spawn eye, dryad limbs, and green stuff.
I also used a small spawn eye to make this third eye. This prince will be dedicated to Tzeentch and I thought the third "mystical" eye was a good way to show that.
I also painted the armor in Thousand Sons colors. However, my Sons are undercoated in black and the prince is undercoated in white. As a consequence, the armor is a lot lighter than my other Thousand Sons. No biggie, I guess.
Here is a rear shot.
Here is a shot of the base before I mounted the mini. As you can see, it has a Rhino door from everyone favorite Dark Angels successor chapter, the Angels of Absolution (Thanks for the painting tutorial, Nick)
Finally, here is a close up of the daemon face on the right arm.