After Curfew

First night at Hogwarts, Rikkali was already feeling restless. She itched to explore the place.
Most of the day she observed. When they were given the rules of the place, she only half listened. There were too many, especially for first years. She hated rules. And these rules, the biggest share of them seemed a bit redundant to her. Some of them were mostly common sense, and even some were absolutely needed. But, for most of them, she couldn't understand why they were created to begin with.
She shrugged those rules off as she quietly slipped from her bed, so as to not wake the others.
It was nearing midnight, the perfect time to go exploring, rules or not. She pulled her black robes over her head, then quietly opened her trunk where her prank stash was hidden within a concealed compartment of her trunk. She took out one of the bags that held her dungbombs within. She then grabbed a second bag, which held various things that would aide in her pulling off the best prank. 'Tonight it shall be dungbombs.' she thought to herself as she closed her trunk and made for the door, grabbing her shoes before heading out. She crept quietly on her bare feet, down to the common room. She remained cautious, in case one of the older students were still up. Peeking into the common room, she gave a soft sigh as it was completely empty. She made her way to an overstuffed chair, sitting down and put her shoes on, then slipped out of the common room into the corridors. She stayed within the shadows, creeping along.
She quietly opened doors and crawled into crevices as well as some nooks and crannies.
She found nothing of interest doing that and quickly became bored. What she really wanted, was to explore the Forbidden Forest. She had heard so much about the place, with all the various creatures living within. She needed the exploration of the castle first though, then the castle grounds, before venturing into the forest. She'd have to observe more, noting times of those patrolling the corridors, as well as the grounds. To do that, she'd have to sneak out a few more times, then expand her exploration out to the grounds and finally beyond into the forest. She will do just that, for now she just has to bide her time.
Rikkali found herself in a dark corridor on the second floor, near the girls' lavatory.
On the floor just outside the girls' lavatory, was a good-sized puddle. The first year had heard about this lavatory long before coming to Hogwarts. Many years prior a young girl had died within that lavatory, becoming a ghost. Being muggle-born as well as for her appearance and having to wear glasses, she had been bullied, causing her to hide within the girls' lavatory, where she had been killed. The girl had been only fourteen at the time of her death. Now, as a ghost, she tends to flood the lavatory, the water seeping out into the corridors.
She stood in the dark corridor, staring at the puddle that seeped from the lavatory.
She then crossed over to a niche in the wall, sitting upon the floor inside the niche, the darkness concealing her. As she sat there, thoughts came on how she could create some prank for anyone walking by. A grin spread across her face. 'A Dungbomb Tripwire. It would be perfect.' she thought to herself. She reached into the bag of prank aides, pulling out a clear string. The string was actually an invisible string. Once in place, she'd have to tap it with her wand to activate the invisibility. She left the dark niche, heading back toward the lavatory. She quickly strung the string across the corridor, this way, those trying to avoid the puddle, would still encounter the string. She then attached the string to a hidden Dungbomb. When the victim crosses the string, it will trigger a foul-smelling distraction. She then tapped the string once, causing invisibility to be activated. She then went back to her little dark niche; glad it was a short distance away from the foul smell that would erupt from her prank. She secretly hoped the Hogwarts Caretaker would be the one who tripped up her prank.
She waited within the dark, watching and listening for someone to come along.
It didn't take long before she heard the shuffling of feet along the floor of the corridor. She peeked out from her hiding place, spotting a shadow. She was unable to tell whether it was indeed the caretaker, a professor, or another student. She grinned mischievously as she waited, hoping to hear a disgusted outcry from the victim.