Legendary actions help, and interesting and useful reactions are important as well, but it is a very rare solo that gets near what the CR suggests is their threat level. Of course,on the opposite end, the encounter rules way overvalue monster numbers, especially weak monsters. There's this illusion of reliable math in the CR and encounter rules that just isn't there and certainly doesn't justify the page count.
That's a peculiar definition of "a challenge" that i don't think many folks would agree with as the minimum requirement. If only a TPK matters that suggests the PCs are anchored to one another or to the world in any significant way.
I take issue with the assumptions built into that "spoiler." You put out a module like this with Soth as an antagonist and you no longer get to say "what happens." That isn't how RPGs work.
Soth has Legendary Actions.
Well, if you have the Odyssey of the Dragonlords: Player's Guide, the Amazon subclass (Ranger) ACTUALLY gives you a Mechanical Bird animal companion. If you don't mind refluffing it to meet the theme and what not, then that's one way of doing it. Also, it's free to download if you don't have it!
www.drivethrurpg.com
Meant for the death dragon
Greater Death Dragons have Legendary Actions.
The DL setting hasn't appeared in an official D&D product for well over a decade, and when it did, the setting did impose restrictions. I don't expect base edition books to mention previous ones, but settings (especially settings that do historically have restrictions) are a different matter.
