System mechanic — not covered elsewhere

The Blood Moon

Roughly one night in twelve, every body of water turns red and the world gets a lot more graphic

The Blood Moon is one of three possible night sky events, decided fresh each night from a seeded table — the same table that also rolls a purely cosmetic coloured nebula (25% of nights) and the far more consequential black hole (15% of nights, the only way to reach the Dream dimension). Being seeded rather than timer-driven means the roll is a pure function of the night number itself: every player's game agrees on what a given night looked like, a returning character's sky is reconstructed rather than re-rolled, and the odds can be checked by counting rather than by playing thousands of nights in a row. Measured over ten thousand simulated nights: 834 blood moons, against a target rate of 8.33% (one night in twelve).

Every body of water turns red

A Blood Moon night reuses the exact shade of red the game's own ending event, the Revelation, permanently stains the sea — deliberately, rather than inventing a second red. The distinction that keeps the two from colliding: the Revelation's red sea is permanent, the Blood Moon's is not, and the game specifically checks your save (not a value that would reset on reload) before letting a Blood Moon's dawn restore the water — so if you actually break the Revelation's seals during a Blood Moon, dawn correctly leaves the sea red rather than accidentally undoing the ending. If the seals were already broken before a given Blood Moon arrives, it never touches the water's colour at all.

Splatter on hits, enemies, and the moon

During a Blood Moon, landing or taking a hit leaves a large blood-splatter decal on the ground — a generated texture (a main pool plus fourteen smaller droplets, since the game uses no image files), capped at 40 decals in the world at once, aging out over time, with the oldest evicted first once the cap is hit. Hitting the same spot again within a couple of seconds doesn't stack a second decal on top of the first.

Every enemy visibly carries the Blood Moon too — three splatter quads applied to each one, angled so at least one is visible from any direction you're standing (a single flat splatter would vanish edge-on the moment you walked around a multi-part enemy model). The moon itself is tinted to match. Everything strips off cleanly at dawn, and the next Blood Moon re-applies it fresh — including to any enemy that's already carrying old splatter from a previous one, so nothing is stuck permanently bloodied after a single night.

Version history

The Blood Moon added: the water tint and the moon tint, from a direct request to reuse the Revelation's existing red-water effect rather than build a second one from scratch. The operator left the exact rate up to the developer.
Blood splatter decals added for hits landed and taken, capped and aged so a long fight can't flood the world with marks or push older ones out through sheer repetition on one spot.
Splatter extended to enemies and the moon, the final piece of the original request — three angled quads per enemy rather than a flat colour tint, since a tinted enemy simply reads as "a red enemy" rather than as splatter.

Trivia

The Blood Moon is deliberately rarer than the cosmetic nebula (1 in 12 nights against 1 in 4) — the design reasoning is that it repaints the whole world, so it needs to stay something you actually notice rather than becoming ordinary weather.
Enemies get their splatter re-applied on every new Blood Moon rather than keeping their very first one forever — confirmed directly by watching a wolf survive two separate Blood Moon nights and picking up a fresh set of splatter quads both times.