After learning that the final task would be a maze, Harry and Cedric spent every free moment they had studying in the library together.
Granger made for a fine assistant when it came to researching general purpose spells which would be useful in a crisis, and she compiled list upon list of spells for Harry and Cedric to study.
Black turned out to be a wealth of information, as well. Cedric began communicating with the convict regularly, at first when the man wrote requesting information which could only be found in spellbooks kept in the Restricted Section of the library. After a few weeks, however, the spells which Black was using - locator spells, mostly - did nothing to reveal the location of Peter Pettigrew or any other active Death Eaters who might have information about what was happening at the school. Therefore, Black began writing to Cedric about ways of keeping Harry safe, various methods of clearing his name without involving Pettigrew, and speculation on who in the school could be trusted and who couldn't.
"Your godfather is kind of horrible," Cedric told Harry, the admiration clear in his tone as he read over one of Black's letters which gave suggestions on how to mess with Moody's head and distract him from involving himself with Harry or the Tournament. "This is psychological warfare, plain and simple. He wants me to gaslight one of our professors."
"Please don't encourage him," Harry replied with a sigh as he glanced up from the spells Hermione had him studying that day. "We're trying to prove him innocent, not provide the Ministry with new reasons to lock him away."
"Harry, your godfather spent over a decade in Azkaban. People don't get better after something like that," Cedric gently explained. "If he was a good person before he was locked away, it's highly unlikely that he's a good person now. Although from the 'real life examples' he gives me for some of these situations, I doubt he was ever a paragon of virtue to begin with. He's smarter than to act on any of his more... reckless or dangerous impulses, at this time, but it's good for him to have some sort of outlet rather than keeping his anger and desperation all bottled up inside."
When Cedric turned his attention away from Black's letter, it was to find Harry frowning at him.
"You think he might hurt someone?" Harry quietly asked.
"Maybe," Cedric replied. "He certainly wants to. He was hurt by a lot of people, and he spent a long time living in a state of hopeless helplessness. That didn't leave him just because he left Azkaban. He's kept himself in check so far, but who knows what might drive him over the edge."
"It's never been like that when he writes to me," Harry argued.
"He loves you," Cedric agreed. "He needs help, yet he's your godfather. He's supposed to be responsible for you, not the other way around. He loves you, and he's afraid of disappointing you or letting you down. That's probably the only thing keeping him in line. So no, he wouldn't write to you about anything like this," Cedric told Harry, motioning to the letter he's recently received from Snuffles. "But it's fine if he writes to me. Especially if he writes with ideas on how to keep Moody out of our hair, how to keep you safe, and how to survive the tournament. Sometimes his ideas are a little... extreme, sure. But even the maddest of ideas have some aspect of value in them."
Groaning, Harry muttered, "Not only are you encouraging him, you're using him."
"Just a little bit," Cedric agreed.
On the morning of the third task, Cedric was horrified to learn that his parents were there, and that they would be attending the task.
He was able to maintain a pleasant smile as he greeted them, at least.
"We're so proud of you, Ced," his father gushed as the man pulled him into a tight hug. "I know you're a bit behind in points right now, but you're a winner, Son. You always have been. You'll knock that cheating Potter boy right out of the running-"
