And therein lies a story. Most magical beasts cannot live in the Mundane world. They instinctively shy away from the crossing, somehow sensing the danger to their very existence. We have very little trouble with them. But certain kinds of creature, certain rather nasty kinds of daemons, can survive over there, although mercifully their capabilities are severely attenuated.
So, let me tell about the one of my less boring experiences. It started on a busy summer's day a few years ago.
I was watching a large and ancient Mercedes coupe inch its way down the arch of the bridge towards the magic-side trap. The car had been retrofitted with domesticated fire daemons, whose heads could be seen emerging from the cowlings over the engine, awoken from their slumber as they re-entered this world.
The vehicle was so wide that other traffic was in difficulties manoeuvring around its low bulk. I was concentrating on directing the horse-drawn wagons and the teams of pack unicorns, struggling with separating the streams of traffic while being deafened by a cacophony comprising, in equal parts, the cries of panicky beasts and the oaths of the carters and working-men.
So, I was momentarily confused and distracted. While my back was turned, so to speak, a clutch of wild tree daemons slipped through to the Mundane world. Now some of you may know these creatures as nymphs or perhaps dryads, but these terms are altogether far too innocent to describe what is really a particularly sneaky and vicious species of vermin.
The daemons were hidden in a shipment of freshly-cut fine timber destined for some specialist cabinet-maker in your world. This kind of luxury item is exported occasionally to Mundane; the resulting caskets prized more for their rarity rather than for any supposed magical properties. The creatures had concealed themselves within the trunks of the cut trees that I had failed to check carefully.
I should have spotted them sooner, but it was too late. I caught a glimpse of them emerging from their hiding places, their scaly heads and curving horns shaking as they freed themselves; their green-and-brown bodies sliding out of the cracks in the bark and the cut surfaces of the solid timber that was roped to the wagon slowly making its way down the arch of the bridge.
I could see that look of malice in their yellow-slitted eyes as they gazed back at me, their gaping mouths filled with brutal teeth seeming to cackle with amusement at my misfortune. The sunlight glinted on ethereal wings which would have allowed them to fly easily in the world of Magic but were shrunken and insignificant in the Mundane world.
The wagon, its driver oblivious to the stowaways behind him, had reached the end of the bridge proper and started along the lengthy causeway towards the coastline of the Mundane world.
The three daemons rose slightly into the air, their wings straining in an environment which is by-and-large anathema to magic. They moved slowly back along the bridge towards me, and I made ready to defend myself with sword and magic.
Then they disappeared - just vanished, before my very eyes.
Daemons have this ability to conceal themselves within the substance that gives them their name - water daemons into streams and rivers, fire daemons into hot solids, and so on. Even our best thinkers cannot entirely explain exactly how they do this, although why is much clearer: it is the ultimate in camouflage, providing concealment until their intended prey is close by.
Tree daemons, as I have already explained, can hide themselves in wood. They need a certain minimum volume of timber to conceal themselves within, so a fully-grown dryad needs the trunk of a mature tree to entirely contain its bulk.
My first thought was that they had returned to the logs they had arrived in. I ran forward, calling out to the waggoner to who had finally realised that there was something happening behind him.
Now, searching for magical creatures in the Mundane world is worryingly hard. The spells and incantations I would have used as a matter of course in the world of Magic were useless over there and, unsurprisingly, there are few technological devices which are effective in the detection of part-Magic animals.
Nevertheless, there are some techniques - tricks of the trade, you might say - which we are trained to use. But I could locate no sign that the daemons were within the logs, or indeed concealing themselves in the wood of the cart itself.
To be doubly sure, I insisted that the wagon was turned around immediately and returned to our world. This was finally achieved with some noisy complaining from the carter, and much struggling with the confused carthorse being forced to back up on the narrow causeway. But it was all to no avail. My charms and invocations revealed nothing hidden in the wagon and its load other than a small cache of gold coins which the driver swore he had lost only yesterday.
In my experience, these daemons do not usually travel far from the crossing, somehow, I think, finding the proximity of the world of Magic a comfort. So I was pretty certain that the creatures had not gone very far.
I set about searching farther afield with the aid of a couple of my colleagues, as well as a small group of Guardians from your world. We must have inspected every wooden vehicle and baulk of driftwood for miles around, but without success. I was beginning to get very worried indeed.
Now, daemons of all kinds are meat-eaters and pack-hunters, and they have a voracious appetite. Over here, these dangerous pests are generally hunted and driven out of populated areas, but every now-and-then a pack finds its way to a farm. They can cause serious losses to livestock. However, they tend to avoid humans, having learned that people are likely to be armed with steel and magic, both of which are - usually - more than a match for teeth and claws.
Visitors to your world are at a serious disadvantage in dealing with wild daemons. We strongly discourage Travellers from taking edged weapons with them into the Mundane world - your civil authorities take a very dim view of strangers wandering the streets armed with swords and daggers, for some reason. And, of course, the thaumaturgalogical defences which would be child's play in the world of Magic are unavailable over there.
I suppose I might have hoped that the daemons had died, or perhaps made their way to some uninhabited region to live on wild deer. If so, then I was sadly mistaken, especially after the first reports of attacks came in.
The daemons started preying on lone Travellers on the causeway on the Mundane side of the crossing early in the morning or late at night. They seemed particularly fond of those poor people who had travelled to your world to seek their fortune in menial work and were returning, richer but often weary, to their family and friends in the world of Magic.
At dusk or dawn, the bodies of returning Visitors would be found dead on the causeway, their faces always twisted in horror and their corpses partially eaten. Other people just disappeared completely - we never found any remains, any sign of what had happened to them. The beasts themselves were never seen. There were no sightings, no reports of unexplained happenings or strange creatures crawling out of the woodwork.
Not surprisingly, traffic on the causeway and bridge started to drop off noticeably. People began to stay away from the crossing, and both trade and tourism suffered badly.
People even began to try other ways to cross between the worlds, despite the well-known dangers from sea and sky. On a couple of occasions, overloaded rowing boats got into difficulties and were the subject of daring rescues by Guardians from both worlds. I was not involved myself, but they were the talk of the Guardhouse afterwards - Guardians are the worst gossips in both worlds, I'm sure of it.
Anyway, I was returning across the causeway one evening, rather later than I had hoped, after another fruitless meeting with the Mundane Guardians hoping to track down the missing dryads.
It was getting quite late in the evening. The sun was low on the horizon, and there were few Travellers about - just a straggling group of walkers, and a couple of horse-and-centaur-drawn wagons returning with their last load of the day.
I had just reached the point where the causeway where the stonework just begins to rise up and segue into the first of the arches of the bridge proper. Somehow I got a sudden impression of something moving behind me. I span around. All three of the daemons had appeared behind me, almost breathing down my neck in their desire to make me their next meal.
The daemons had been hiding in the massive timbers that formed the floor over the Mundane trap. I mentally kicked myself for overlooking this possibility, and I had always known that the worn timbers were easily mistaken for stonework. Thinking back, the point where the dryads had disappeared was right over the centre of the trap.
The creatures seemed to have grown in size since I last saw them and were now the largest daemons I have ever seen - they had evidently been well-fed over the last few weeks. I drew my sword, although it seemed like a toothpick compared to the overgrown man-eaters I was facing.
I'm a firm believer that discretion is the better part of valour. I backed away, waving my sword to keep them at a distance, then turned and ran, shouting at the Travellers to warn them. The people and the smarter kind of working animals scattered immediately, the dumber creatures being dragged or whipped into rapid movement.
An idea flashed through my mind. I dashed towards the magic trap on the other side of the arches of the Old Bridge, desperately trying to remember the precise series of incantations which would trigger its demolition, incantations I never seriously expected to use in earnest. The daemons followed closely, moving alarmingly quickly despite their atrophied wings.
As I rushed over the flowing orange sprites of the Magic trap, I began to shout out the syllables which activated the transition. My timing had to be perfect, so that I was clear of the area while the daemons were still close to the centre of the trap.
There was a soft whump and a roar of wind as the trap was sprung. I fell to the ground, clinging desperately to the flagstones with my fingernails in an effort not to be dragged into the vortex I had created behind me. My trusty sword had fallen at my side, and was sucked clanking into the hole in space I had opened up.
The activated trap acts as a kind of drain into nothingness - a 'suction pump', a 'Hoover', as previous Visitors have described it. The frightful creatures were ensnared, drawn howling into the whirlpool of magic, never to be seen again.
So, now the crossing is safe once more. We no longer allow motorised vehicles or other large transport on the causeway, and we are much more careful with screening goods in transit. You will have seen that we have re-instated the Magic trap, as you passed over it on your walk across the bridge.
Have a good day, and enjoy the rest of your visit to the world of Magic.