Planet Aniaros Primus was covered with a variety of difficult terrains; from soft sand dunes about the equator, to rough and broken rocky plateaus to thick, uneven jungle and huge bogs. Name a type of terrain that is hard to traverse, and it was there. It was also positioned in a very important intersection of several space-lanes. Controlled by the Imperium, it was a home away from home for a battalion of Imperial guardsmen; there, just so the other races didn't take control.
There was nothing else of note on this planet, or in it's system; a lone planet about a small white star. No interesting flora or fauna, militarily speaking. No valuable mineral deposits. Nothing but the (admittedly variable) difficult terrain. The planet was safe because it was so uninteresting to everyone.

A lone landspeeder skimmed the tops of the trees, the green-upon-green canopy stretched to the horizon in all directions. Both occupants dozed as the craft flew a set patrol course for the umpteenth time. Nothing changed, nothing was ever found. The planet was tidally locked to it's star and moved in such a uniform orbit that there were no day/night cycles and no seasons. Sensors on the craft scanned the surroundings and recorded logs that were remarkably similar time and time again. The ecosystem was in such a perfect balance that it would be fascinating to someone interested in that kind of thing (as would many things), but in an age of war there is no such person.

After their 12 standard-hour shift had finished, they returned to base, passing the next shift at the boundary fence. The occupants only looking forward to a proper kip, they left the craft in it's hangar for the servitor to download the data and service the craft. 3 hours later, they were stood in front of their superior trying to come up with excuses to why they didn't notice when the craft's sensors signalled a reading 9 hours into their shift.

The reading was a single, simple electronic signature; that which might originate from a vehicle. This piece of excitement did occur on occasion, when a sensor was in error, or a random tree may have fallen over, or one of the occupants of the craft snored too loudly. However, error was ruled out and the current shift was roused after about an hour of attempts to contact them. They were directed to the area to see if a tree had fallen over and to then continue with their route.

Seven hours later, when the second landspeeder didn't return, the following shift was sent with specific instructions to find the missing craft. This type of excitement had happened only once before, when a snoozing pilot had shifted position and his knee had hit the controls, sending the craft into a dive.

It wasn't long before the search crew radioed in a report of a column of smoke and an electronic signature not far from the apparent crash-site. They were ordered to investigate the signal and report back immediately. When no report was forthcoming and the landspeeder could not be contacted the base commander was informed and a plan of action was proposed; a ground-based unit would investigate the area in question as they couldn't risk loosing any more landspeeders if there was something (natural, artificial, daemonic, etc.) knocking things out of the air. You can't be knocked out of the air if you are not in the air, was the rationale.

Unlike anywhere else in the galaxy, there was no shortage of volunteers for the operation; boredom will do that to people. Within 2 hours the unit was complete, as was a second unit that would accompany them (many volunteers, you see), and they set off to the last known coordinates of the landspeeders. They would take at least 2 full 24 standard-hour "days" to reach the area and another day to find the one known "crash" site.

The jungle floor was sparse of plants due to the density of the canopy, but it was dense with discarded branches, twigs and leaves. The ground was uneven, rising and falling by meters within the length of a groundcar. The trees were too close for most tanks to be of use, so the men had to march on foot. As expected, they found nothing for 3 days.

On the morning (as designated by time, as the sun never sets in this area) of the 4th day the men picked up the scent of burnt plastic and metal, and scanners finally picked up a signal for an inorganic mass ahead. 30 minutes later they spotted the wreckage of the second landspeeder through the tree trunks, highlighted by the light falling through the hole in the canopy that they must have left.

The occupants were dead on impact, the craft was bent and twisted, but it was noticed on many of the surfaces the signs of gunfire; bullet-holes peppered the craft and were of a calibre comparable to that of an assault cannon. This was no accident, the men spread out to form a cordon about the crash site, looking outwards. Men from the second unit started patrolling the surrounding area. In spite of the density of the trees, visibility is generally good in this jungle; the rough terrain can be seen to stretch for 100 or more metres in all directions, only split into vertical lines by the multitude of tree trunks. Every man scanned his field of vision for anything that was not a tree.

After a short while the patrols found markings indicating movement, scattered with gun casings. The markings were confusing though; They weren't the tracks of tanks or wheeled vehicles. They were "footprints", but not of infantry, the feet were large enough for a man to sit in and the depth indicated the weight of a tank. Some trees had been knocked aside, but not in any straight paths. Whatever this was it could navigate between the trees.

Both the Eldar and Tau use walking constructs in warfare, but no matches could be found on record or memory to the footprints the men could see. They found no other tracks, was this... thing working alone? Were there more? and most important of all, where was it? Thoughts also turned to tyranids as clouds moved in overhead, casting a dulled lighting over the men. They felt exposed.

One of the scanners took that moment to pick up another signal, to the east. The men formed ranks and split into their respective units. They moved quietly, alert to danger, towards the signal. It was inorganic, like the earlier signal, but the cloud cover meant it was more difficult to make out shapes broken up as they are by the trees. The eyes began to play tricks on the men, helped by shadows in the gloom. Soon, it became apparent that there was a shape ahead; low and wide. The units spread out and moved in a pincer movement upon the shape. As they approached, it was noted that a couple of trees in that area had been knocked over. They readied their weapons and continued to approach.

A break in the clouds above sent a spear of light through the break in the canopy and revealed a scene of carnage... the crash site of the first landspeeder. One of the greener recruits fired into the wreckage reflexively, he got a firm talking to by his sergeant and the men relaxed a little and moved to secure and study the site.

It was different to the earlier site; the pieces of wreckage were smaller, there were no signs of gunfire. This craft had exploded and many smaller pieces could be see stretching off into the distance indicating that it had broken up in flight. The surrounding area yielded no clues this time.

The men followed the path of the wreckage in a hope of finding the attacker's position. They remained alert, but found nothing. Then it happened...

There was a whoosh, a thud in the distance, and then an explosion that sent men flying in many directions, not all of them were whole men. There was panic, they ran in all directions; the men that had not seen much fighting ran towards the threat, those that had seen a great deal of fighting ran the other way (there's a 6th sense that tells you when you're on the loosing side in a fight that hasn't started, and it's time to regroup... elsewhere).

Then there was movement between the trees. A few men spotted it at first, and more caught sight as lasgun fire was directed that way. There was something large, very large, moving this way and that. It was possibly twice the width of any basic tank and seemed, to those that had seen one, almost the height of an imperial knight titan. But it moved and changed direction impossibly quickly on the terrain.

As it got closer the colour could be made out; it was mainly a light, creamy-bone colour, with areas in bright orange. It's shape seemed to morph and twist as it navigated the ground. This time the men saw the flash and heard the thud before the whoosh and explosion. Another group of men were scattered across the leaf litter... in bloody chunks. Those still alive retuned fire to no apparent effect.

Closer still, and the shape became distinct; it was spider-like. Long legs extended from it's sides and it had 2 appendages at the front that were waving about erratically. Behind it's "body" was a tall domed shape that was obviously the turret. The thing, now identifiable as a "walking" tank was doing anything but walking... it was hopping, skipping, jumping, and running between the trees, it's legs dancing across the rough ground in a way that could only be compared to the multi-legged tyranids. But this tank was heavy, it would demolish any tree that got in it's way without slowing down, and it was big; the legs were long enough that a space marine could walk under the body without needing to duck.

Now it had got into small-arms range, and the men could hear it talking as it closed the distance. What they heard was a childish voice that had a robotic/synthetic undertone, and it was saying things along the lines of:
"Are you part of the test?"
"I didn't know I'd have playmates"
"You must be target practice, right?"
"I thought I'd get closer to try these..."
With that, the tank aimed it's arms towards the men, 3-fingered "hands" opened up and a pair of 3-barreled Gatling cannons spun up and fired into the throng, tearing men apart.
"Hello, am I doing good?"
Close up, the tank had the appearance of a scorpion; the arms out front spreading death as efficiently as any claw, the legs (only 4) steepled out to it's corners giving a solid firing base but moving fluidly, and a long tail curling up from the rear of the body and tipped with a main gun suitable for any tank, ready to sting it's prey.
"Ooo, is that what I think it is?"
One of the men had aimed a missile launcher at the tank, the guiding laser played across the tank's body. Suddenly, rods emerged from the top of the tank and lasers danced around the surrounding area. Before anyone could stop him, the missile launcher fired and the missile began an erratic flight as it tried to lock on to the many laser sources. It nearly hit several trees and then one of the tank's lasers fixed onto the bearer of the missile launcher, all the other lasers moved to focus on him and the missile duly followed. He ran, but he didn't get far.

The massacre continued for a further 5 minutes. The men were now running and hiding for their lives; any thoughts of fighting back had been replaced with surviving and escaping.
The tank had also changed tactics. It was now standing very still, surrounded by the bodies of the fallen, and pivoting on the spot whenever someone moved from behind a tree. It seemed to be able to see in all directions as men tried their luck when the tank's back was turned, only to be caught by fire before they reached the next tree.

It soon became a stalemate as those that moved didn't live to tell about it.
"Oh, I love hide and seek... lets see here"
The tank would push over a random tree and then gun down anyone that was exposed.
"Are you still there?"
Working outwards, the tank was creating a clearing in the jungle.
After about 20 minutes there was a clearing large enough to land a Stormraven, and the tank wandered off having not found anyone for 5 minutes.
"Booooooooooooooooooored"
After the noise of the receding tank had faded, 3 men crawled from their hiding places. They made their way back to base as quietly and as quickly as possible.

Days later, the men reported to the commander and he contacted the high command asking for backup.
Due to the report only mentioning a single tank, that had not shown any sign of greater forces, and had not threatened the base of operations, the backup received was less than had been expected: Large squads of guardsmen were better used in full battles, the space marines were too busy to go searching a planet for one tank and due to the terrain no vehicles were of any use. What arrived, months later, was a lone assassin.

His papers, that he handed directly to the commander, stated that he was "the best" at what he did, and had declined a "holiday" on Catachan to come and hunt a tank. The commander was dubious of what this assassin would achieve, but as the tank had not shown up since the massacre, he wasn't going to argue with a face like a mountain.

The sniper headed out into the jungle in a tight-fitting bodysuit that seemed to be made of the stuff of shadows; not black, that would stand out, but it sucked at the light that fell on it. As soon as he passed the first trees surrounding the base, he disappeared into the gloom. He carried a huge, scoped rifle. Powerful enough to penetrate the thickest of armour and accurate enough to hit a man in the eye from over a mile away... in the right hands.

It took at least a month of searching for the sniper to find the tank. He had been tracking it for 12 days so far. It had moved from the jungle where the massacre had happened, north into a more mountainous region with fewer trees, but more shrubs and bushes; ideal for the sniper.
He observed the tank at first, through some basic binoculars, noting it's mannerisms.

The tank was moving about the terrain, seemingly at random. It had mentioned "testing" during the attack, and so the sniper assumed that the tank was just being tested in varying terrain environs. He swapped his binoculars for the scope of his rifle to get a closer look and to start getting a "feel" for the tank's movement.

Linking to a variety of satellites in orbit, the scope of his rifle adjusted automatically to air density, humidity, wind, and even gravitational variations. His mind was also linked to the scope so that he could process all the data and pick the perfect shot.

He zoomed in to get a good look at the tank, searching for weak spots, as he came to consider the white dome towards the front of the body of the tank it swivelled and 3 black dots, in a triangle, came to "look" straight at him through his scope. The sniper quickly zoomed out to see the whole tank and noticed that the turret had also rotated to point at him. He moved, as swift as a tyranid, and gained as much distance as possible from his position... which exploded as a shell landed where he had been hidden seconds before.

Finding a ridge, out of sight of the tank, the sniper moved to another hidden position that the tank couldn't trace him to by extrapolation. He then had time to think about what had happened; The tank had only noticed him after he had started using his scope. It wouldn't be len-flare or his movement, his kit was too good to give away his position like that. The tank had to have access to the exact same satellites that his scope did; it had seen the uplink and triangulated his position. Had he known this, the sniper would have used the same trick to find the tank. He would have to do this the old-fashioned way from now on.

Switching his scope into "dumb" mode (it would only act as a simple lens scope now) the sniper repositioned again to get a view of the tank. It had moved to examine the crater where the sniper had been spotted. As predicted, the tank then followed the path taken by the sniper to the ridge, it looked about briefly and then moved on apparently giving up on searching.

The sniper followed the tank's movement and continued to study for weaknesses. Judging by how quickly the tank can react, he would only have one good shot at disabling it before retaliation. The sniper noted the position of the hatch, on top of the tank, and from that looked for places to penetrate into the operator's cockpit. As large as the tank was, the shape and size of the main body was only large enough for 1 or 2 crew. The best point he could see to attack was next to the headlight/spotlight. At the point it was attached to the body it was likely about head-height and roughly central to the possible cockpit; attacking at just the right angle the bullet would penetrate at the join for the light (rather than having to penetrate an unknown thickness of armour) and pass through one or both of the crew. He waited for the perfect angle...

The sniper let the tank move further away, this would give him time to fire a second shot into the armour affording a second possible chance to kill one of the crew. But without his satellite link neither shot would be as perfect as he would normally achieve. He also did not take his aiming drug, further harming his chances, as if the first 2 shots did not disable the tank he would have to move quickly to avoid return fire. He took a breath, and squeezed the trigger...

The first shot struck true, the tank flinched and popped smoke. The sniper's second shot was blind into the smoke. He saw the sparks of the glancing bullet through the smoke, and then the tank emerged from one side of the cloud, facing his direction, and immediately fired it's Gatling guns. The sniper dived behind a rock he had chosen for cover, the surrounding area was raked with gunfire.

In a break of the fire, the sniper repositioned to his secondary position, where he may be able to get a third shot. As he turned to reacquire his target he saw the tank had closed the distance, running and leaping over the terrain; it was well practiced indeed. He took a quick shot, and the tank dodged the shot, again the bullet glanced off the armour harmlessly. The tank returned fire from it's Gatling guns. The sniper ran for the cover of some trees.

A tree behind him exploded in a shower of splinters and fire, the sniper fell to the ground'; shoved by the shockwave. Ears ringing and with his back feeling like it had been scattered by a thousand red-hot knives, he pulled himself up and ran on to find cover. He waited for any signs of movement and when he sensed none he peered from the shadow of the tree. He could see the remains of the shattered tree and beyond, the rocky terrain.

Over the ringing in his ears he heard a child-like voice behind him.
"What are you looking for?"
He turned, but was too slow, a huge hand pinned him against the tree, the barrels of a Galting gun pressed into his stomach. He felt ribs crack and heard the tree creak under the pressure. He couldn't breathe as he looked up into the 3 black eyes in the large white orb. The eyes rotated this way and that, regarding him.
"It's a good thing that there is no one in my cockpit. You could have hurt someone"
The pressure increased and the sniper felt his heart beating in his throat. The surroundings became grey and then black and the last thing he saw were those 3 black dots.