How the Blood Moon works

Contrary to popular belief, the Blood Moon does not flat-out “respawn everything”. In fact, there are only 2 things it respawns: equipment and enemies, and not even ALL of them as there are a lot of exceptions and special cases (listed farther down).

When and how do Blood Moons happen:

Blood Moons are on a strict schedule of 2 hours and 48 minutes of active IRL playtime. “Inactive” playtime, like when you’re in a menu, loading screen, cutscene or dialogue, do not count for this, so you sadly can’t just pause the game for 3 hours to force a Blood Moon to happen.

Nothing ever speeds up that timer:

There are still a bunch of long disproven rumors floating around the internet that you can allegedly make the Blood Moon come faster by killing a lot of enemies or using up a lot of resources (like breaking ore deposits, picking fruit, breaking barrels) but this does not influence the timer at all. And some other “tricks” even make the entire process take LONGER, like repeatedly skipping nights at a campfire - the little “Link crouches down in front of the fire and the screen goes dark” thing counts as a cutscene, which means that the Blood Moon timer STOPS during those few seconds and only continues to run after you gain control of Link again… and if you then immediatly interact with the campfire again, the timer won’t have advanced at all. It’s an easy way to turn a 3 hour waiting period into a frustrating 17 hour fiasco.

You can however delay the Blood Moon:

If you are inside of a shrine, Divine Beast or any other area that prevents the Blood Moon from actually happening (like Hyrule Castle, the Trial of the Sword, the DLC One-Hit Obliterator trial, certain minigames etc.) then the red moon will rise but simply fade into a regular full moon at midnight (regardless of which moon phase was actually due that night - it was probably just easier to animate). No cutscene, no revival. The event is then automatically rescheduled to the following night, where the Blood Moon will attempt to happen again.

In theory, you can infinitely repeat this as long as you just skip each and every Blood Moon. I’ve once skipped 101 in a row for a challenge run and nothing out of the ordinary happened (the run went super boring super fast tho as you’re running out of enemies and equipment after a while).

There is also a slight glitch(?) with fast travel:

This one requires precise timing. If you manage to teleport the very moment the Blood Moon cutscene would otherwise start - at midnight sharp - then you won’t get the cutscene at all. The game then pretends that the cutscene HAS happened (malice particles still rising from the ground for a few seconds) and the timer starts over again (meaning you now have 2 hours and 48 minutes before the next Blood Moon happens) but since the actual cutscene was skipped, nothing respawned.

What does and does not respawn?

The Blood Moon is responsible for regular non-boss enemies, as well as weapons/bows/shields that are NOT inside of a chest. That’s it. Everything else either respawns under a myriad of wildly different other conditions, or not at all.

And there are a lot of exceptions and special cases as well:

Exceptions: Monsters/Enemies

Master Kohga and the Blights never respawn. You are able to refight the Blights in the “illusory” rematches from the DLC Champions’ Ballad as often as you want tho, because those never actually DEspawn, meaning that you don’t need to wait for a Blood Moon in order to fight them again and again. The same goes for Ganon and Monk Maz Koshia: they never actually vanish and can be refought as often as you want, whenever you want, independendly from the Blood Moon cycle.
MINIbosses like Hinoxes and Taluses however respawn every Blood Moon, including DLC minibosses like the Molduking and Igneo Talus Titan.
Some enemies perpetually respawn without the need for a Blood Moon, like the monsters inside the Trial of the Sword (revive every time you restart the trial) and Eventide Island (revive very time the zone is reloaded). The latter still happens after the trial, so every time you save & reload ALL monsters on the island will be back immediatly.
Enemies that are generated randomly, like most Stals, Chuchus or Octoroks, do not need a Blood Moon either. Basically everything that pops out of the ground falls into this category.
The same goes for SOME Lizalfoes. Most of them have stationary spawn locations (need a Blood Moon) but there are also randomly generated ones swimming in the ocean and rivers / lakes (mostly blue ones) and the Electric Lizals jumping out of the ground in the Gerudo Desert. The latter two do not need the Blood Moon to spawn.
The disguised “Travelers” that turn out to be Yiga Footsoldiers need the Blood Moon to respawn, as they are stationary. Yiga Archers and Blademasters ambushing you without warning are randomly generated and do NOT need the Blood Moon to respawn.
Even tho Bokoblins normally revive: The Rider Bokoblins from the “Horseback Hoodlums” quest stay dead once you completed the quest. This is likely because they would otherwise interfere with the hurdle jumping minigame you unlock, as it takes place in their former territory.
…an amusing/awkward non-exception is that those are the ONLY quest-related enemies that stay dead. There are a lot of quests that require you to wipe out entire enemy camps (Take Back the Sea, The Sheep Rustlers etc.) or even minibosses (Face the Frost Talus, the Giant at Rali’s Pond etc.) but it is enough to have killed the respective foe(s) at least once. The questgiver will give you the same loot and dialogue anyway even if the monsters are alive again by the time you collect your reward.
All Guardian Scouts inside of shrines respawn, no matter whether it is a puzzle shrine or a “Test of Strength” one - except for the tutorial scout in Kakariko. Once you completed Ta’Loh Naeg’s Teaching, that scout will never reappear.
There is a single Bokoblin next to the Great Plateau Tower, who vanishes entirely after you activated the tower. You don’t even need to defeat him.
Hostile animals like bears / wolves, despite attacking the player, do not count as “enemies” and aren’t affected by the Blood Moon.

Exceptions: Equipment

The Master Sword doesn’t respawn in the pedestral once you obtained it, otherwise you could get multiple indestructible weapons permanently blocking inventory slots.
The Ceremonial Trident under the bridge in Zora’s Domain. If you want a replacement, you need to reforge it, just like with the Lightscale Trident.
Even tho BOWS respawn, ARROWS will not. If you, for example, pick all Shock Arrows from the trees on Ploymus Mountain, they will be gone for the remainder of the playthrough.
Equipment on Eventide Island respawns every time the zone is reloaded. This is likely a safety measure so the player can’t run out of resources during the trial. It still works AFTER the trial as well, but that might be an oversight.
The same goes for items and enemies in the Trial of the Sword.
If an item is inside of a chest, the chest overrides the respawn mechanic. A looted chest[^1] will never respawn, regardless of whether or not the item inside was actually programmed a different way. For example, the Hylian Shield WOULD normally respawn every Blood Moon, but since it is inside of a chest and chests never respawn, the shield won’t either.

Bonus: Guaranteed Critical Success while Cooking

Another useful thing the Blood Moon does, is provide guaranteed crits for every meal that is able to crit[^2]. Any eligible meal cooked between 23:30 and 00:15 on a Blood Moon night[^3] will get one of the following:

+3 additional red hearts
+1 additional yellow heart
+2 “units” extra stamina (green or yellow, depending on the dish)
+5 min extra duration
+1 tier extra effect (like Lv.2 Flame Res instead of Lv.1)

Which ones are possible depends on the dish. A “hearty” meal for example is already fullheal 100% guaranteed so it won’t get extra red hearts on top of that, and it doesn’t have a timed effect so no extra tier or extra duration. A meal with a timed effect (like Shock Res, Cold Res etc.) can get extra duration, an extra tier OR red hearts, but won’t ever get the stamina boost … and the tier will never exceed the limit, so you won’t get things like Lv.4 Attack Up. It sill caps at Lv.3 either way.

For the “Under a Red Moon” quest:

…there is already an extra guide. ;)

Footnotes:

[^1]: A chest will count as “looted” only if you actually took the item out of it. If you open the chest while your inventory is already full, Link will close the chest again and the game will act as if you never touched the chest. It will not DEspawn until you actually loot it. An exception to this are amiibo chests, which will vanish every time the zone is reloaded, regardless of whether or not you looted them. And chests always only respawn in their default positions, meaning that if you move an unlooted metal chest with magesis halfway across the map and then save & reload, the chest will be back where you originally obtained it, NOT where you dropped it.

[^2]: It does not work with Dubious Food, Rock-Hard Food, and for whatever reason, Fairy Tonic. Using Monster Extract randomizes the attributes and prevents crits from happening. And there are also items that guarantee crits already (Dragon Horn Shards, Star Fragments) and you can only get ONE crit at a time, so using those for Blood Moon cooking is a waste.

[^3]: The guaranteed crit window is from 23:30 to 00:15 but if you save & reload after midnight, the effect will end early and meals will no longer recieve guaranteed crits (tho you may get a “random” one if you’re lucky)