Okay so I'm going to attempt to write my first story in the Marauders era since they are definitely before Harry's time and my apologies if this is sucky.
"A map of Hogwarts?" Remus Lupin said raising his eyebrow as he stared at the blank parchment in front of him as he looked at his best friends James Potter and Sirius Black who were both grinning at him.
"Come on Moony," Sirius said smiling. "If we work together, we're sure to come up with something and it'd help us so much in pranking. You're the best in Charms, so we thought you'd be able to come up with protective enchantments so no one but us could read it."
Remus pondered this. Protective enchantments…a map could be useful, not only in pranking but for better methods at not getting caught. "One enchantment that would be good is for it not to be fooled by the Polyjuice Potion. Another would be secret passwords obviously only we know." He began muttering a few charms that he knew to increase protections of it. "Sirius, can you draw up the maps to the Secret Passages? You're the best at drawing out of us. Prongs, you come up with the passwords. Peter…" He hesitated. "You can be here to give us all a moral boost."
Peter nodded eagerly as the other three Marauders got to work. Remus looked through his Charms book to add as many protective enchantments that he could find. It had to be ensured that only those who knew the password could read it and anyone else who tried, there would be a code to ensure that they couldn't reach or access the map. In order to add to the protections of it, Remus added a drop of the Polfors potion which would help the map to look like a common bit of parchment.
Sirius was also deep in thought as he drew out small lines to where the Secret passages led from to Hogsmeade and from to come into the school. It would be useful to have it drawn out especially since Peter often got lost trying to get to Hogsmeade without the rest of them. This was so exciting…making a map of Hogwarts along with the Invisibility cloak would really aid in their pranking. Besides, Remus was prefect and this would give him extra ways for them to not get caught causing trouble.
"Ooh, maybe I should draw a path that leads to the forbidden forest too," Sirius said eagerly and Remus paused in his enchantments for a moment to look up at his best friend.
"Of course, but the forest is still within Hogwarts so drawing out the passages to Hogsmeade might be a lot better," Remus offered and once Sirius nodded, he got back to working out the protective enchantments.
"We'll use our nicknames on the map so if it ever gets nicked away, no one will know that it's us," James mused to himself. "Messrs. Moony, Wormtail, Padfoot and Prongs. It's only natural your name comes first Moony, since you're coming up with ways to protect the map and keep it from getting caught and for it to be flawless. I mean, what's the charm that manages to fool Polyjuice?"
"It's a complicated one," Remus admitted. "But Professor Flitwick taught us it in the previous class so I managed to remember it besides I read up all about it in the library and just now in my Charms book to make sure I got it right. I think I'm almost done with the enchantments though so Prongs do you have the passwords ready?"
James nodded. "Yep. The password to open the map is I solemnly swear I am up to no good. I think it's fitting since we're pranksters and we're using it to aid us in our pranks and all. Then to close it off so no one else can read it 'Mischief Managed' since it's managed into a map." He looked immensely proud that he had come up with a logic for each password and Remus looked happy about it too.
"Good, you can use your brain and put logic to use," Remus teased his friend causing James to pout.
"Hey! Of course I can use my brain," James said indignantly. "I just don't need to do it in class because I can always ask you if I miss anything."
"Oh is that what I'm reduced to?" Remus joked. "Your encyclopeodia?"
"I…what?" James said having no idea of the Muggle term that Remus had just muttered.
"It's a book with all the informations of the world," Sirius explained, coming forward with his maps. "Ok, so I have all eight passageways, the entrance to the Shrieking Shack and the Whomping Willow all drawn out. How are we going to put this all together?"
Peter was staring wide-eyed at Sirius's drawings. "How are we going to arrange this into a map though? It needs names of students and everything."
Remus chuckled at how impressed Peter looked. "It's simple, Peter. A small identification charm with an expansion charm added to it and it can recognize pretty much anyone in Hogwarts without us having to do much. Okay, so we're ready to put this all into action." He turned back to his book, flicking through pages faster than anyone had ever seen him do before and began working his charms as Sirius's drawings came to life flitting perfectly into the map like structure and while the lines that Sirius had drawn had disappeared, the way to the passageways was clear, at least to the Marauders because they had explored them properly. There…the Marauders Map was made.
"This was bloody brilliant," James said beaming. "We made a map of Hogwarts and it's all thanks to you Moony."
Sirius pouted a little. "Hey, I helped."
Remus chuckled, cheeks going a little pink at the compliment. "Yes you did. I didn't know the passageways as clear as you after all and James, the passwords are genius and your insult idea works well too. So in order to celebrate the creation of the Marauders Map," he touched his wand to it. "I solemnly swear I am up to no good."