Tzitzimitl
About
They are up there all the time and the sunlight is the only thing holding them off. During an eclipse the light fails and they come down, skeletal and enormous, wearing skulls at the wrists and ankles, to finish the world and everyone in it. This is not a metaphor in the places that believe it. It is why the drums start, and why everyone makes as much noise as possible, and why nobody is permitted to stand quietly and watch.
Stats
Save Rolls
Traits
Special Attack
It can act only while the sun is obscured, and it does nothing at all at any other time. Claws: slashing, melee 15 ft, +6 to hit, 3d8+6, twice each round. Devour the Light: 40 ft, save Wis Mind, fail save roll 3d8+6 necrotic, cooldown 2 rounds, and any non-magical light source within the radius goes out and cannot be relit while it lives.
Special Defense
Only in the Dark: in direct sunlight it cannot act, cannot attack and cannot remain - it withdraws upward immediately, whatever its HP. The encounter has a hard clock, and the clock is astronomical, and the DN should tell the party exactly how long the eclipse lasts. Reduced to 0 HP it comes apart into bone and falls, and there are a great many more of them. Noise: the traditional response works - drums, shouting, anything loud and communal - and while the din is kept up it takes 1d10 at the start of each of its turns and will not close with the source.