Sorry for the horrendous english.
This was made by Jospeh Campbell and was slighty changed along time creating new formulations.
A lot of stories follow this formulation even inadvertently, for example: Star Wars, Undertale, Matrix, Finding Nemo etc...
But how does this work?
The image above tells a clockwise rotation of a base story.
NiNoKuni uses the Monomyth exaggeratedly so i'll be using NiNoKuni a lot for examples, if you have more examples let me know in the comments.
(Im going to explain this with my words, If you want to check this out by yourself google it)
The hero is selected or called by something to start a adventure
Sometimes the Call of an Adventure has a Rejection of going to an Adventure but it finally leads to the hero finally accepting the call.
Example: Ni No Kuni 1
The hero meets someone who will help him in his journey because he knows the world where his adventure will begin.
Example: Ni No Kuni 1 (Drippy), Majora's Mask (Navi), Undertale (Toriel), Deltarune (Ralsei), Akinomoriš(Parme-San)
Where the hero leaves his normal life and his past him and starts his journey.
Example: Ni No Kuni (The creation of the magic portal to the other world)
Here, the hero will be subdued to different feats to prepare himself for the new world.
Example: Ni No Kuni (Oliver looking for pages of the Magic Book and the magic wands)
The hero will find someone with powers or a wise man who will confirm to him that he is the chosen one.
Example: Ni No Kuni (Again) (Old Father Oak), Zelda - Ocarina of Time (That old tree who is dying)
The hero is doing all of this for something or someone, and the "Woman" is the reward (This is very metaphoric)
Example: Dragon Quest 8 (Lift up Medea's Curse), Almost every Zelda (Zelda lmao), Ni No Kuni (Save his mother)
I don't really understand this one but the father figure sometimes is the one who has the power to decide between life or death. Or is just the acceptation of Son-Father so the son is able to go on.
Examples (No NiNoKuni this time but major spoilers for Dragon Quest 8):
Evangelion: Shinji wanting his father being proud of him, Dragon Quest 8 when the hero finally meets his father figure, Munchie.
Is when someone in the story dies, I don't really know how to explain this one.
It is what the hero has been striving for in his journey.
The "elixir" is what it is called in the monomyth, the object, power or knowledge for which the hero has been fighting, this elixir can serve many things in a story: Save the world, end the darkness, save yourself, save someone...
Example: Dragon Quest 8 (Lift up the Trodain curse) Evangelion (Shinji receiving the knowledge that he matters in the world)
Since this is the end of the story this might change a lot depending on the story, but the campbell formulation is:
After having found happiness and enlightenment in the other world, the hero shares his gift with the people in his world.
Example: Ni No Kuni Movie
The rest is kinda postgame, but if you liked this blog and wanted to know more about the rest of the Monomyth post a comment :)
A lot of stories uses this monomyth thing a lot! Maybe you didn't knew.
The way the monomyth is used is not literal.