The possession pipe sounded like the most entertaining option, fifteen minutes didn't seem like much but it'll be more than enough to mess with those bothersome girls.
Gilgamesh waited for the right moment to strike, he kept quiet as the girls started walking away, chatting and laughing about all the trivial activities they'll do once their school day was over.
Their little conversation was interrupted when they entered their classroom, Gil couldn't help but smirk as he saw that, one of the most utterly tedious parts of being a child was attending class, something he could avoid but Illya couldn't, but he was about to... compensate her for that.
He grabbed the magical pipe and shoot a dart straight into her neck, and as soon as it made contact with the girl's skin his perspective shifted, he was no longer hiding in a corner and stalking that annoying little girl, now he was standing in the doorframe, exactly where she was.
"Hehehe" A brief chuckle left his lips as he looked down and saw Illya's small frame dressed in that bland white shirt and black skirt, a dull uniform for a dull school.
Fortunately for all these bored kids he was about to make things livelier, he walked to Illya's desk, which was close enough to her friends' own desks, and decided to jump on top of it.
"Listen everyone!" Gil exclaimed as he extended his arms up, waving at the students to get their attention, something he soon achieved and before long every single head had turned and at Illya's desk.
Once he was sure he got everyone's eyes on him he started with his entertainment, which he kicked off by literally kicking the desk, jumping up and down as he started shouting, "Attention fellow students! I have an important message for all of you!"
As the words left the little god's lips gossip spread through the room, each student in the room was already mumbling to each other what this weird 'girl' could want, most probably hoping it would be something important enough to make them lose some class time, and he wasn't going to disappoint.
"I, Illyasviel von Einzbern, am a massive weirdo!" he roared, spreading his arms as if he were the letter, T, "I'm a weirdo, a massive dweeb who spends the entire day watching anime and wishing I could be a magical girl!"
After 'Illya' exclaimed that the whole room erupted into laughter, each boy and girl present in this little classroom started cackling as they pointed their fingers at the weird white-haired girl, the only ones who abstained from mocking her were her friends... well at least most of them.
The four he did not know but wanted to 'go shopping' with the little mongrel were holding back a laugh, fighting with their urges to join the crowd, the only one who remained steadfast in her support from her friend was Miyu.
Gil couldn't let that stand, if Miyu wasn't going to laugh he was going to turn her into a laughing matter, "But there's one girl even more pathetic than me!" he pointed a finger at the black-haired girl, "Miyu Edelfert! She wants to act all mature and smart but she's a bigger dweeb than me!"
He jumped off the desk and started looking through Illya's backpack and a smirk soon formed in his visage when he saw a certain magical wand, "Look!" he shouted as he picked Ruby up and hold her over her head, "She even bought me wand so I can play magical girl with her! We spend hours and hours cosplaying and pretending we throw spells at each other, isn't that right, Magical Miyu?"
"Illya..." Miyu mumbled, her cheeks turned red as she saw all eyes were now laying on her, and her embarrassment only grew when the whole class broke into laughter once more, and she had no choice but to bury her face in her hands.
The sight was priceless, and Gil couldn't be more glad the fifteen minutes limit ran out at that moment.
Back outside the room he couldn't help but chuckle as he heard the laughter of the kids being interrupted by a shriek, curious to see Illya's reaction he decided to walk back to her classroom.
Once in the doorframe he slightly opened the door, after all, he didn't want all the mongrels to be distracted by a 'door that opened by itself', then he poked his head inside the room and saw the fruit of his hard work.
Illya was still shrieking, she had shown Ruby back inside her backpack but was struggling to close the zipper, "There's nothing suspicious here! Absolutely nothing weird going on! Just continue with the class!"
Unfortunately for Gil, the fun was not to last, he felt how someone passed next to him as the door was opened and when he tilted his head he saw a woman he assumed to be Illya's teacher, a young woman with short brown hair.
"Class~" she cooed as she entered the room, with two stacks of paper in each hand, slightly shaking them to catch her student's attention but as she saw they were ignoring her she decided to take a more... drastic action.
The teacher picked up a large eraser and slammed it against the floor.
PLOP
"Ahhhhhhhhh!" the laughing was interrupted by a collective shock the whole class finally notice their teacher was there and started behaving as they should in that type of situation, straight back and looking forward, ready for whatever she was going to teach today.
The only one who didn't pay the teacher any attention was Illya... who was still fighting her bag's zipper, "Go up! Go up!" she begged, unaware of the woman who was walking towards her.
The teacher stealthy made her way to Illya's desk, none of the students turned in her direction for they knew what was about to happen, warning Illya was pointless... she was already doomed...
"Illya!" the teacher shouted as she slammed her hands on the girl's desk.
"Ahhhhhhhhh!" the unexpected way of greeting her was more than enough to get Illya's attention who started mimicking her classmate's former reaction.
"Why so rude, young lady? Your teacher enters the classroom and you can even say hi?"
"Uhh... h-hi Taiga..." the girl managed to stutter.
"What did I tell you about calling me Taiga!" Taiga yelled as she pressed her face against the girl's, and she planned to keep staring at her until she went back on that rude use of her name, but something in the corner of her eye caught her attention.
"What's this?" the teacher asked as she picked up Illya's open backpack, "Why did you bring this to school?" she retrieved Ruby and held it up, allowing everyone to see the kaleidostick.
Illya gasped at that, it was bad enough she had gone momentarily mad and showed everyone her wand but now Taiga had it... she was the only adult she knew that might try to actually use it... she had to get it back now!
"Please give it back Miss Fujimura!" she cried, but her begging was met by a sheet of paper being shown on her desk.
"You'll get your toy back after the test Illya! So turn that frown upside-down because it's test time! And it's your favorite subject, English!" Taiga turned around, dashed to her own desk, left Ruby there and picked up the other sheets of paper which she started delivering through the room, an act that was followed by a collective sighing.
Gil started stroking his chin as he saw the scene unfolding in front of him, this unexpected turn of events presented him with a few new ways of messing with Illya...
He could possess her teacher and make things even harder for her, or maybe wait until the test was over and mess with her personally... the other kids in the room could also help with that goal, especially her friends, he could already imagine her sobbing after being bullied by Miyu...
In the end, Gilgamesh decided to...