Thank you so very much for your in-depth analysis and review, I really appreciate your insights, and I agree that its emphasis on failure, Fumbles, Omens, and the like all make Catastrophants potentially annoyingly difficult adversaries.
For what it’s worth, I myself wouldn’t use a Catastrophant as anything other than a boss, and most interestingly as a campaign-wide threat. I imagine a kingdom suffering from a Catastrophant’s curse unknowingly, desperate for seers to understand why the most significant figures continue to fall victim to bizarre and deadly accidents. The player characters would be aware of this looming threat in the background between adventures, until eventually they too begin to suffer, and must launch into an investigation that culminates into a showdown, maybe even at the dawn of a new misery that is ushered in by these heralds of the Two Headed Basilisk.