With every failed time spell, the magister grows a bit more paranoid - or perhaps it's not paranoia, since the Elder One really will kill him for his failures. The distinction hardly matters. After the tenth failure, he began locking himself in the great hall during his waking hours. After the twentieth, he had the foot soldiers excavate a shard doorway from parts unknown and painstakingly install it in the castle.
Now, his most "trusted" assistants can only see him if we all go at once, together... which we must do twice a day to bring him his meals, as he never leaves that room at all.
This text can be found in Redcliffe Castle in Dragon Age: Inquisition during In Hushed Whispers. It is not included in the Codex. The note can be can be found in the Upper Royal Wing. Upon entering a corridor, enter the first door on the right.