Saleen spent over 1,000 years training to use lightning magic in a rather boring way before seeing signs of advancement. The powerful beings he surrounded himself with were shocked. They gathered around him and wanted to see how a mage like him could advance.
"It's dangerous. Leave me alone!" Saleen barked. The only people left around him were the three weapon spirits and the Violet Angel. They wanted to say something to him, but he chased them all away again and again.
His followers knew he was not one to make a bigger deal out of things than they were. If he said something was dangerous, it was definitely something that could affect their lives.
This was why a mage's advancement was generally not witnessed by others.
If enemies observed the process, they would be able to assess a mage's true powers. If friends were watching from the sidelines, a failed advancement might cost them their lives.