A funny thing you can notice about the Great Runes is that all of them are altered by something — all of them except Morgott’s.
If you look closely, you can see that Morgott’s Great Rune is the only one that looks exactly like the Elden Ring itself.
Rykard’s rune is twisted with the blasphemous serpent.
If you read the item description: "A Great Rune of the shardbearer Rykard. Its blessing restores HP upon defeating enemies. Rykard was among the children of Rennala and Radagon, who became demigod stepchildren after Radagon's union with Queen Marika. But Rykard fed himself to the blasphemous serpent - Great Rune and all."
He literally fed both himself and his Great Rune to the serpent.
Let’s not even talk about Miquella’s Great Rune. :]
For Mohg, it’s kinda cool because he managed to use his blood and merge it with his Great Rune.
He’s the only one who actually managed to change the nature of his Great Rune. As it says in the item description:
"But Mohg's rune is soaked in accursed blood, from his devout love for the wretched mire that he was born into far below the earth."
As for Radahn — he’s kinda helpless in this game. His Great Rune is the only thing keeping him from completely rotting away.
in item description its said:
The Great Rune burns, to resist the encroachment of the scarlet rot.(radahn great rune)
With Malenia, it’s similar, but the difference is that her rune is becoming one with the Scarlet Rot, while Radahn’s rune is being destroyed by it.
here comes the hard part:
Rennala’s Great Rune is also altered. She used it so many times that it’s getting weaker and seems to be losing its light.
The same thing can be said for Godrick’s Great Rune — it’s getting weaker too, and it’s golden ray is turning yellow.
but why morgott never used it?
i think it's because he doesn't see himself worthy of using his mother's legacy, like he is afraid to curse his great rune with his omen blood
