Janus day

Jermander walked towards the Singleton Quad not really paying attention to the things around him.  He knew most of the buildings on the way, and they were predominantly lecture halls and administrative buildings, so there wasn't very much activity either inside or outside of them.  He automatically detoured away from the Dragonlair, where Gorillamumps's Chancellor lived, but everyone did that.  The Chancellor was much-rumoured, much-feared, and never seen.  He skirted a small cluster of Mushroom Pups, the young of the Fungi from Yuggoth.  They smelled strange to him, a kind of chemical, preservative odour that made him think of embalming fluid gone somehow wrong, and when he was a bat they had a completely different shape in sonar than they did to his eyes.  They were otherwise popular though, as they always had the latest versions of the latest gadgets.  Sometimes ahead of the shops.  Finally he felt the ground vibrating through his feet and knew that the Left-aligned Ancients of MuMu were having one of their late-night chanting sessions.  He sat down to think.
Janus day.  Janus day was tomorrow, and he'd not even considered what he was going to do for it.  He had a vague memory of someone, a teacher probably, telling him that Janus day was also known as New Year's Day, but he couldn't remember which of the many New Years that the humans celebrated it was.  He rather hoped it was the one with the colourful paper dragons and fireworks as it was very easy to find prey on that one, but he had a feeling it was one of the duller ones instead.  For the undead, and the students at Gorillamumps, Janus day was something else entirely.
On Janus day lots of the portals and doorways between worlds opened.  Exactly which ones opened depended on the year, or more precisely, the Earth's location relative to everything else.  There were some that always opened: the portals to the Astral Realm were hard to keep closed at the best of times and impossible on Janus Day, and the Elemental and Astrological Houses were just as keen.  Some hardly ever opened: the portal to the Minion Realm opened once every thirty years and so the Minion Market only happened that frequently too, but equally the doorway to the Throne of Elder Things only opened once every fifty-thousand years and no-one really wanted to be around when that next happened.  The problem was never so much things coming through, as being able to push things back, and fifty-thousand years was a long time to improvise a prison for.  They still had another twenty-thousand years to wait before they had a chance to push all the humans back to where they came from, after all.
Normally Jermander liked to celebrate Janus day by hopping up to the fourth dimension and meeting up with his extended family; in the fourth dimension they could all travel just a short distance from anywhere in the world and meet up, making it very convenient.  Sometimes he and his cousins would pop over to the Elemental realms and borrow a couple of Elemental Pets to let loose in the houses of enemies and friends as a little Janus day prank, and sometimes everyone would just drink heavily until closing hour, and then they'd try and remember the way home.  Someone would always get lost and end up on the wrong continent, and Jermander looked forwards to the letters from home telling him who'd done it this time and how long it had taken them to get back.
This year was his first at Gorillamumps though, and he really wanted to do something that would let the campus know that Jermander was here, that he was someone to keep an eye on, that he was going places.  The Blistermas Herpes prank was a good start, but he couldn't stand out in the open and claim that one, he'd have to let people work it out for themselves, and although underground praise was good, it wasn't enough.  What could he do for Janus-day that would be remembered for years to come?
Still musing he turned himself into a bat, and felt dizzy for a few moments.  Thankfully, this time it wore off, and he fluttered up to the eaves of the dormitory of the Left-aligned Ancients of MuMu and listened in to their conversation.
"...the cobordism of souls necessarily requires an unbarrelled space and a pointed group," said a deep, resonant voice.  There was a noise like the tapping of a wooden stick on paper.  "In fact, the homological integral over seven fractal dimensions doesn't exist unless the group is pointed."
"Are you really integrating with respect to a Solomonic Seal?" asked another voice, which though just as deep had feminine qualities.  "Is that completely justified?"
Hah! thought Jermander.  I should totally find a Solomonic Seal and let that loose on the campus!
A moment later he fluttered down from his perch in the eaves and transformed back into himself on the lawn.  As usual, his clothes transformed back with him but in piles on the ground, and he had to hurriedly dress himself before anyone looked out of a window and saw him.  But that was it, that was what he could do for Janus day.  Go the Astrological Houses and 'borrow' Taurus for the day and leave him on campus while he went drinking!