Hehe, there’s a thread on the RU forum called “Why Mortarion?” I’ll give a slightly more detailed answer here. A long time ago, when I discovered Warhammer 40k, I became interested in everything related to it, including music. And then I came across the song “Keepers of Death - The Saga of Mortarion.” I’ll say right away that the song is really bad, it’s not easy to listen to, but I liked the lyrics.
If anyone's interested in listening, but it's really bad, I've warned you.
Text for everyone else.
I was born amidst a terrible slaughter,
Nurgle then took root within me.
I grew in a cave, among darkness and plants,
But I dreamed of a life without the friction of war.
I am like a flower, grown from the mud,
The dark princes became my enemy.
My cage has rotted, now I am free,
I am not fit for slave chains.
The one who raised me like a beast,
Suffered long in torment,
When Barbaros became almost mine,
He knew I was coming for his head!
A star tore through the black sky,
Barbaros illuminated it with its light,
It was the Emperor on wings of steel,
The crowd suddenly called me his son.
A pact was made between God and me,
That I will endure the gaze of Mother Death,
Otherwise my world will become his alone,
Otherwise I will serve him my whole life.
Alone I climbed the mountain of bones,
Prepared to fight my father-prince.
The battle between death and me was swift,
And I fell to my knees before the star.
The Emperor came, slew the prince,
Protected me with his wing,
As promised, I swore to him.
But secretly I decided that I would have vengeance.
I accepted the gifts; before me stood the Legion,
The Death Guard, they called themselves.
“To the Crusade!” the Emperor said,
Like a loyal son, I carried out the order.
I gave him hundreds of worlds,
I asked for no praise in return.
I am a free flower, no place for me in a cage,
No, I am different, I am made of different stuff.
The Warmaster said we would be free,
Horus whispered we were like birds,
A plan for overthrow blossomed in our hearts,
The Emperor will soon know the pain of his fall.
The golden collar fell from my neck,
New truths I then learned.
I washed my face in the blood of brothers, sons,
Eternal sorrow—such is my sentence.
Horus the brother leads me to the liar,
Into the warp, to Terra, the fleet sails.
The rustling of the night suddenly became a chorus,
I stood before the Black Throne.
My children suffered in torment,
Both mind and flesh knew the pain of hell.
Eyes flowed from their sockets,
Souls left the soldiers’ bodies.
The plague consumed my guardsmen,
The disease slowed my pulse like a black poison,
When liquid pus began to flow in my veins,
I almost choked on a wave of despair.
Typhus, the handsome one, gathered all his strength,
He rose up alone against the swarm.
I am your father, Legion, step with me,
I will lead you to another life.
Nurgle’s words:
Accept my essence, Mortarion,
You need no more false crowns.
I will spare your Legion’s life,
Let your fleet join another pyron.
A groan of despair filled my throat,
And my Legion was already among the graves.
My children were almost dead,
I fell helpless upon the carpets of intestines.
Yes! I swear, but spare me from suffering.
Preserve my Legion from wandering.
Let the Death Guard live forever,
Where I am, all is perishable and fleeting.
Hell has ended, the disease has become beautiful,
The Legion’s fate is simply terrible.
What once killed us has become useful,
Now we no longer belong among the weak.
I am like a child again, like a hunted beast,
From this black cage I cannot escape.
My new master is my father,
In the womb of Mother Death I found my end.
Now my children live even in death,
Their sweet faces are forever twisted.
My Legion has become a plague-sore,
I lead them in suffering, Primarch Mortarion…
Mortarion!
-Son of Death!
Mortarion!
-Beloved of Nurgle!
Mortarion!
-The ruin of our hopes!
Mortarion!
-Black-winged Primarch!
And so the plague fleet hovered over Terra,
The Dark Primarch returned to the control room for an encore.
The lump of despair continued to grow,
Through tears, the daemon whispered, “Forgive me.”
So, thanks to the song, I became interested in this character and his story. I got really into him and decided to take this nickname.