A Gate-threshold flares and someone else steps into the room. "Allow me, please." He takes over with the scrying-focus, throwing much more complex magic into it, scanning the area where the alarm must have originated. 

In a valley in the mountain where those alarms were tripped, there is a crater. Partially buried in the ground at the center of the crater is something that looks like - an enormous turtle whose head is made of chrome and whose back is made of glass, except that no glass could possibly have survived that impact. The maybe-glass is currently opaque. 

After a minute a door opens in the chrome part of the turtle. A bird flies out.

A minute after that, six tall, distinctly nonhuman creatures with bladed limbs depart through the door and start walking around the outside of the giant turtle, smearing mud on it and bringing over underbrush to lean against it and slashing through trees to bring them over and lean them against it too. It's going to take them a long time because it's a very enormous turtle but the aim is quite plainly to leave no obvious signs of it.

Well. Interesting. 

For now he won't reveal that he's noticed their arrival, but people are going to be scrying the area very closely around the clock from now onward. 

Leareth gets out the artifact that helps him cast at a distance, and lays a hemisphere of passive wards around and over the turtle-thing, undetectable to anyone without mage-gift, but sensitive enough to alarm if anything larger than a deer moves across the boundary. 

The first bird comes back. More birds leave. 

The blade-creatures stay close to their turtle, felling a dozen more trees to drag over and conceal it. 

Are they magic birds. 

Nope! They are not magical at all.

Fine casting at a distance is very difficult and almost no one but Leareth would be able to do it, even with the artifact setup. He attempts to hook a little ribbon of magic to one of the birds, invisible and intangible except to mage-sight, but durable enough to last a few days and it'll let him recognize the same bird again, and hopefully, trace where it goes. 

It goes off south in the direction of the nearest village. 

Leareth leaves someone else watching it while he drops some similar tags of magic on the now-half-concealed metal and glass turtle, and also tries to get as close an examination of it as possible. 

There's no apparent hinge at the place where the chrome sometimes folds open to reveal a door, and the door seems to open into a chrome antechamber just large enough for two of the bigger-than-human people to stand in which does not itself have other doors, or at least they're never open simultaneously. Half the turtle is buried in the dirt where it landed, but it looks like it might have fins like a fish rather than limbs like a turtle. The exterior looks in various places scorched, in addition to smashed in the landing. There are some dents and some streaks like a bolt corroded partway through the chrome.

The person watching the bird informs him that the bird is turning into a blue horseman???

What? Leareth is over in the room again seconds later, looking for himself. 

Blue horse-men is about right! They're four-legged but also have arms, and have a long bladed tail more than the length of their body, and have additional eyes on stalks, and have no mouth and an odd snoutlike nose. 

They're hanging out in a forest. They seem to spend a while just resting.

Leareth's expression is very level but his thoughts contain escalating levels of 'what???' 

Does one of the blue horsepeople still have a bit of magic marking them, from when they were a bird? Leareth will try marking all of them again anyway, they don't seem to have mage-sight or at least aren't reacting to it. 

After a while one of them turns into something smaller, thin-skinned and frog-like though it's the size of a housecat. The transformation process is grotesque; the skin bubbles and the bones visibly shift around and the skin goes translucent in time to watch the organs stretch and distort.

None of this is magic at all though it is, if one thinks to look, interacting with other planes a lot.

...the other one takes a few cautious steps forward through the trees and then fires an energy weapon of some kind that's also not magic at the nearest human.

Leareth badly wants a closer look, he can sense some of the weird interplanar shifting going on, but scrying at this distances loses a lot of resolution for mage-sight and it's murky. 

He doesn't know their capabilities, though, so he stays where he is. His expression doesn't change at all when the strange, vaguely levinbolt-like but nonmagical weapon fires; he just watches to see what happens to the young woman next. 

They drag her into the forest. 

The one that's still a centaur-thing turns into - her. 

There is a brief conversation. 

It shoots her again and drags her back out to where she was, after checking to make sure no one else saw it. 

Leareth asks someone to watch and make sure she wakes up again. He keeps his attention on the centaur-thing, in particular waiting to see if his magic markers will stay put over all the body-shifting. He suspects they will; it's the same life-force, it's just having very strange things done to it. 

The things turn back into centaurs, rest, and then turn back into birds. His magic markers do stay put; apparently whatever is being swapped between planes in such an elaborate fashion isn't the lifeforce. 

They fly back.

The turtle has almost entirely vanished beneath felled trees, at this point. 

Leareth is viscerally hungry to stick a Healer in front of one of them and find out what their Sight can pick up on. It's not even magic, strictly speaking - maybe some sort of unheard-of, highly specialized Gift...? 

He does not immediately Gate any Healers out to look. Instead he uses his communications-spell artifact to contact a dozen people in other locations, makes sure the area is under high-alert scrying coverage, and then goes to get some rest until something else major happens. 

Over the crashed ship, the sun is setting. 

It's not worth working on hiding the ship at night, the lights might be conspicuous. The people who haven't been dispatched on additional acquisition or spy missions stay in their ship, try to repair some of their equipment, sleep in shifts, pace their Dome.

Nothing alert-worthy happens until the morning.

A small group of people travels south overnight, hoping to get near enough Haven they can make the rest of the distance in morph in the morning.

The rutted dirt track running alongside the river becomes a wider gravel road. They reach the border with Valdemar a hundred and some miles later. There's a military barracks there and some bored night sentries watching the river for unauthorized boats and the road (which shortly later turns into a properly paved road) for unauthorized carts traffic. 

They'll find some forested area away from the sentries, if that can be found, to cross through. They can jump rivers and do not especially benefit from roads.

Then they can pretty easily make it past unseen. 

A couple of drifting vrondi air-elementals notice the magical flags placed on them earlier and drift over, but it's not nearly enough mage-power to meet the alarm threshold and they drift away again, bored, and also invisible to anyone without mage-sight. 

The settlements are much larger and more frequent now, though still interspersed with regions of untamed forest. The next town has an entire main street with two-storey wooden buildings, and a watermill.