TLDR:

In addition to being a "bridge" between the Lands Between and Shadowlands due to affiliation with the Formless Mother, Mogh was the twin brother of Morgott the Omen King, who confronted and fought Radahn, when he tried to invade Layndell during its second siege.

And since Miquella viewed Radahn as his Consort even despite his fails to overcome challenges of his own (aiding in the Starscourge conflict, got saved by his own army from Margitt), he decided to "improve" his Consort by putting Radahn's soul into the body of Mohg the Omen, the body of the same creature, as Morgott.

Alas, by doing so, and constantly helping Radahn, Miquella created a warrior not worthy of the Consort's title.

What makes one a worthy Elden Lord and God's Consort?

It's plain and simple: these titles are earned by being the strongest of all, and defeating all of your opponents and enemies, so then later you could be the defender of your Land, your God and its Order, and provide the best lineage possible.

*Godfrey, the first Elden Lord* tells us, if he kills our Tarnished as *Hoarah Loux* :

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And he says the same, when we kill him:

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And when Godfrey defeated all of his worthy opponents, Marika divested him and his army of their Grace, and sent them to fight elsewhere to grow stronger in the face of death, so their Grace would be returned for them to win the Elden Ring back, and earn the titles and responsibilities of the Elden Lord and Marika's Consort once more.

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* - Elden Lord Crown:*

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* - Third Church of Marika*

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* - Church of Pilgrimage*

All, that Godfrey achieved to become an Elden Lord, was done by his own strength alone.

It's not enough to become the Elden Lord once, so after you could just sit on your throne, all nice and comfy.

You need to constantly improve yourself on your own, because it is your job to defend your God against countless foes, as an Elden Lord and a Consort, not vise versa.

Radahn definitely got this "might makes right" message.

This is why Godfrey was his role model. He even called himself the Lord of the battlefield's Lion in contrast to Champion's cub (Radagon's son). And that also didn't stop him from being proud of Radagon's heritage and features, like his red hair. He earned a title of General, and leaned the gravitational magic not just to help his scrawny steed, but to use it in his battles.

So, Radahn really was almost set up for success.

And it was the Starscourge conflict, that gave Radahn his fame of being the mightest among the Demigods:

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* - Starscourge Heirloom*

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*- War councilor Iji*

The Greatswords of Radahn hint, that his fame wasn't earned by his own strength alone.

After our fight with the Promised Consort, we get our hands on his black steel swords, that he got in his youth right before he arrested the starry skies:

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The sudden appearance of these swords seems to be something of a divine intervention to aid Radahn in his battle with the Stars.

And the skills of these Swords all contain Miquella's light incantations:

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* - Promiced Consort skill*

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* - Lightspeed Slash skill*

And the line about not relying on just a physical strength and gravity spells, the things, that Radahn was known for, heavily hint, that Radahn was secretly and heavily aided by Miquella during his fight with the Stars.

Radahn and Margitt the Fell Omen fight:

During the second siege of Layndell, that we can read about on the stone sword monument near the Outer Wall battlegrounds, Margitt the Fell Omen was stacking piles of hero bodies, and thus the Erdtree and the Capital were left untaken.

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When we start our New Game, we see the painting of Margitt pinning down young Radahn, piercing him with his cursed sword. The both are surrounded by an army, and one of the soldiers is holding his sword too close to Margitt's body.

But why no one mentions this in the game, except the painting? The mightiest of the Demigods being bested by an Omen?

Such thing could be never put to song.

Miquella understands, that some things should never be revealed to a broad public, like Marika's destruction of the Hornsent's society. Or that his desired Consort was bested by a son of the first Elden Lord, as it is Radahn who is supposed to be the strongest of all for that title.

I believe, that the fight between Radahn and Margitt was a one-on-one stand off at first, Radahn's attempt to prove his worthiness of the Elden Lord title. And when things got dicey, or Miquella simply being not so sure of Radahn's strength, he sent Redmanes to Layndell to aid their Lord, and later completely forget about such occasion.

After all, Miquella is able to control the minds of people:

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- the Bewitching Branch

We can find Miquella's lily right in front of the Stonesword Monument in the remembrance of the second siege of Layndell, where Margitt is being mentioned.

And we find a lot of Miquella's lilies right next to Caelid castles, like Gaol, where a whole squad of 2 mages, 4 soldiers, and 1 huge Pumpkin Head guy are thinking, whether or not they should burn this rotting pile, if the precious flower is right next to it. In addition, this is a place, where we find Starscourge Heirloom talisman, of all places. Or a lily right next to the Redmane's castle.

All of that hints, that Miquella the Empyrean visited these places on some occasions.

Mohg the Omen, Lord of Blood

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*- Sir Ansbach after researching the Secret Right scroll*

So, like my title and TLDR suggest, Mohg was a perfect vessel for Consort's soul, because he represents the creature, that bested Radahn, and he's Morgott's twin, which makes it all even better. Plus, his affiliation with the Blood God, that later would be used as a mean to nurture Miquella back to his strength after he embedded himself into the Haligtree. All it took is charming Mohg into thinking, that Miquella will take him into his Consorts.

Miquella's disservice

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* - Remembrance of a God and a Lord*

By constantly aiding Radahn in his greatest battles and obstacles, Miquella made a huge mistake of haulting Radahn's growth as a true warrior. He was still a strong opponent, but sadly, it wasn't enough to earn the crown by legitimate means. And Miquella knows that well. This is why he descends upon Radahn's back to aid him in a battle once more.

And this is why he is trying to kill us, because our Tarnished is a living proof, that there's only one thing behind Radahn's title of a Consort. And it is not his strength, but a mere wish of a powerful Demigod-child.

Just IMAGINE this scene in the movie:

In the heat of a grand battle Radahn gets bodied by Margit. He falls down, as the Omen jumps on him, trying to pierce his Lion armor with his fiery cursed sword.

Radahn is struggling to push it away, and his armor is starting to actually char... When one of his soldiers puts a sword to Margit's throat, threatening to kill him, unless he releases their Lord.

And Margit complies, leaving his mark on Radahn's chest piece side as a reminder of his defeat.

That would be so cool to see in cinema T_T

Quick remark: sometimes I see, how people call Miquella's curse "the eternal nascency", when in reality it is called "the eternal childhood":

>Miquella and Malenia are both the children of a single god. As such they are both Empyreans, but suffered afflictions from birth. One was cursed with eternal childhood, and the other harbored rot within.

*-Remembrance of the Rot Goddess*

Nascency refers to the birth, origin, or early beginning of something. It signifies the state of coming into existence or the very initial phase of development, so pushing from the Nascent Butterfly item description this means, that *these butterflies specifically signify his Haligtree rebirth, not his curse.*

We know for sure, that before Haligtree, Miquella was already a formed child, but constantly balancing on the verge of growing up. We can track that by looking at the Haligtree statues, where first we see Miquella being a bit smaller, than Malenia, and then she grows up into a towering woman, while Miquella still remained an itty Demigodling due to his *curse of eternal childhood*.

So, before the Haligtree supposed rebirth, he was leaving St Trina's lilies at his points of interest as his alter ego, then there were the Miquella's lilies, which symbolize the faith in Haligtree (that I speculate to be just the Trina's flowers, but blessed with his Empyrean blood, hence the green buds on those lilies), and then we got the Butterflies after Mohg... forcefully halted Miquella's full Haligtree rebirth, lets call it this way.

The opening cutscene of the base game shows us Miquella being taken out of his first cocoon, and being covered in little transparent wings. And some kind of a veil on his head, just like on St Trina in the SOTE trailer cutscene, so I speculate, that this could also symbolize shedding her influence by leaving these butterflies. That reminds me a bit of how Malenia didn't accept her Rotten butterflies as well, and only Romina took them as her own:

>The scarlet butterflies are as the Goddess of Rot's wings. Bereft of a master, they were soothed by Romina, who reached out to them.

This theory can be used in tracking of Miquella's timing in his travelling across the Lands Between, and who knows, may be we'll finally understand, how did those 2 Butterflies end up near the Chapel of Anticipation next to some gold like splatter (these can be found through out the whole Grafted Scion arena), where we start our own journey. Also, there are 3 of them in the Shadow Realm, of all of the places, nor far from the Temple Town Ruins.

Thank you for your attention, let me know what do you think:)