Sauron was terrified! He looked at Lex in horror.
He had no doubt about Lex's ability, but he could not be promoted to a sorcerer due to money. The speed of practice was originally slow and he had to figure out ways to earn money. That took up a lot of time.
He was already sixty-eight years old. Although he had another good forty to fifty years of life, according to his progress speed, he would not have any hope of promoting before he died.
Promoting to grade-7 sorcerer, his lifespan would be lengthened for another century. Even if he stopped there, his lifespan would have been doubled!
Sauron was convinced. He could not refuse such a thing.
"My only condition is that this would be a secret between us." Lex had a poker face on.