Let's see....Scorpion kills the original Sub-Zero in the first tournament. Sub-Zero's soul was tainted with evil and he descended into the Netherrealm, free from compassion. He became Noob Saibot and offered his alleigance to Shinnok and Quan Chi and he became a member of the Brotherhood of the Shadow.

basically the original Sub-Zero become some thing similare to Scorpion. Scorpion wasnt always as he is right now. he didnt even go by the name "Scorpion" b4 he was killed i dont believe. when he was killed he became the spectre known as Scorpion. a spectre is another word for ghost. then when Subby died he became Noob Saibot who is a wraith. im not sure but i think a wraith is pretty much same thing as a spectre.

its actually pretty obviouse......

Actually the two words meaning are vastly different. And Scorpion was indeed calld Scorpion before his death. His true name is however Hanzo Hazashi.

k i wasnt sure if he was called Scorpion b4 his death or not cuz i couldnt stand to play Mythologies. and in this case there isnt really much of a difference between Scorpion and Noob Saibot really.

In Sub-Zero Mythologies, Raiden told Sub-Zero to beware of the Brotherhood because they can lure in new recuits or something like that. When Sub died he went to the Netherrealm because of his crimes, and joined the Brotherhood, thus creating the wraith Noob Saibot.

I think that he joined the Brotherhood because in Sub Mythos he had a "thing" with Sareena, a member of the Brotherhood. So maybe when he died she convinced him to join. Just a thought.

And when I looked up specter and wraith, they are about the same. Same synonyms at least.

She couldn't have convinced him to join since she hated and abandoned the clan and was banished to 5th Plane of the Netherealm at the time. I doubt she knows he was turned into Noob Saibot.

I believe Sub-Zero was turned into Noob Saibot against his will. In Mythologies Quan Chi and Shinnok wanted Sub-Zero join the Brotherhood, but he refused.
He later beats Quan Chi and steals Shinnok's Amulet. So they send Scorpion to kill him and when he dies he gets sent to the Netherealm. And what's the ultimate punishment? Turn him into exactly what he didn't want to be: their mindless slave.

Very true, Sad but true.

Oh I didn't know the whole story to Sareena. Where does it reveal that she was banished to the 5th plane?

In MK:Tournament Edition. After her human form was destroyed by Shinnok, she was banished to 5th Plane as punishment for betraying the Brotherhood.

My theory: Sub Zero is sentenced to The Netherrealm for his crimes as a living being. He is stuck there, without a way out like Scorpion had. Before he can find a portal out, The Brotherhood attacks and kidnaps him. He is brought before Quan Chi and Shinnok. They know how skilled and ruthless he is. They offer a way out of that horrible realm and in return he is their agent in the living realms. He accepts and they make him Noob Saibot. My personal theory.