So, this guy was, by far, the hardest Titan to spawn. I easily spent over 50 hours in different spots with a box AFK killing everything (targetting with F8 then hitting pet attack constantly). I looked at the Magelo spawn points and had him placed in multiple of the most promising looking ones. I tried out the spot listed on P99 as well. All with no luck.
Then, I came back to ZAM and studied the picture of him with the two boulders and the mountain peak. I ran around until I found that area (approximately 2966, 1624, 995) and I camped there with my pet, facing south. Within two hours of camping here, Slyder the Ancient popped. Now, maybe this is just coincidence and the joy of RNG, but I would suggest trying that spot first.