You sit back in a vaguely metaphorical sense and wait for time to pass. You think you've done a pretty good job so far! Everything should more or less turn out fine for your cute little creatures. With all the prosperity and ore you've been providing them, you're expecting an Age of Craft or a Age of Wealth. Something like that, surely.
Having made your Pact with the spirits of the world, you have instructed them all that they may inflict violence upon your chosen people in the name of self-defence. This command filters through the back-doors of the minds of every spirit in the world, passed along in a chain of communication that is only sometimes misinterpreted. And that is why when the Spear Clan continues their aggressive mining operations to strip the steel off the surface of the filament in the bare patches along the beach, the steel spirits rise up and start murdering them. Their homes are under attack after all. This is the cause of great upheaval and the start of a prolonged conflict known as the Steel War. Hundreds, thousands, of Lek-kego die in the early days of it as steel spirits stalk the sands and rip people limb from limb. They don't have it all their way of course, as the fabric of their own essence form the Spear Clan's own shells, weapons and fortifications. The Spear Clan retreats to its domes and its forts, with dead and dying steel-spirits spiked out in front to ward off others. The outlying lands are lost and all communication with their newly formed colony on the other side of the beach is severed. Many proclaim this the darkest days and the end of Lek-kego civilisation, having practically forgotten that other Lek-kego once existed at all.
Though the spirits do not immediately attack the Remnant Clans, minor tungsten elementals do incorporate to warn them of the effects of the new Pact. They are attacked by the Knights but, due to their status as, well, tungsten, they aren't killed as much as they are warded off. A small time later, they and some of their friends strike back in a massive counter-attack! Seeing the futility of their fight, many of the Knights flee off the tungsten plains and take refuge in their ancestral holdings around the lake atop the solitary island. Many of the other families are permitted to join them as they use precious supplies of iron and a lot of the tungsten they have left to construct a fortress on the lake's edge. The lingerers, the slow and those who saw this as an opportunity to escape the Knight's rule are left behind to be mauled. And with that, the spirits are sated. The Remnant Clans cease to exist as a functional and diverse society and just become the Knights of the Lake and their collection of serfs, who know first-hand now what they need the Knights to protect them from.
The Spur Clan survives the effects of the Pact unscathed thanks to their ability to speak with and bond with spirits. They entreat the earth spirits for their permission to continue to mine and the expeditions to the Plateau continue. Though they have to climb to its metallic top, they waste no time in carving tunnels through the solid gemstone and crystal mix that makes up its bottom layers. Some of the gems quarried are kept in their original shapes to serve as crude baubles and are later carved/melted into clumsy but beautiful statues and monuments, with a spire of solid ruby being erected in the edge of the marsh where the Founding Heirophant was said to have first spoke to the spirits. But most of the gemstones are melted down to their composite minerals such as aluminium, beryl, carbon and a lot of trace elements, some of which have magnetic traces that wind up in their shells and colour them various bright shades. To bear these wavy bands of colour quickly becomes a sought-after status symbol. The spirits of the Plateau object to this and refuse communication but against the Spur Clan spiritualists and their tame spirits, there is little they can do.
The Knights continue to fortify their island keep, only sending out quick scouts to recover tungsten ore from the now forbidden plains below. But with the construction of the keep and with the lack of access to most of the Shard, they have run out of iron for breeding and shell-repair. Some of the serfs start stripping parts of the fort and are executed whenever they are found. This doesn't stop some of the Knights doing the same of course. Small amounts of iron will be taken from safe parts of the fort and rationed out from the Knights to the serfs, using a reverse form of the tithe-taking they had devised but only for the purpose of shell maintenance. Breeding is punishable by death.
The Steel War continues with the Spear Clan, having lasted now for several generations of off-again on-again sporadic conflicts. The Spear Clan has shrunk immensely but will continue to fight, devising means to slay steel spirits and continue mining where it can. It is discovered that steel spirits are less likely to harm Lek-kego with high percentages of steel in their shell and since this generally consists of the high-caste Lek-kego and nobody else, the Chieftain of the time controversially puts many of them to work. What are they going to do, deny military service? But as a result, several 'steelshells' start plotting to collude with the spirits outside, planning on using their connection with them to stage a coup. A new idealogy begins to flourish among resentful steelshells, one that stems from the caste system and the previous tradition of using steel for class-identification. It tells them that Lek-kego with steel in their shells are superior and that the others are just trying to drag them down and undo them.
The Spear Clan colony, incidentally, still lives though it has been generations since they were able to contact or get reports from the main body of the Spear Clan due to steel-spirits roaming the sands. They are under attack as well of course, being right by the edge of the beach and before the endless steel plains of the filament. But this has not stopped them from thriving, taking the attacks as a perverse pleasure that only increases their resolve and their sense of fervent identity as the Spear Clan. Even if they are the only 'Spear Clan' many of them have ever known. They have their own Chieftain now and have had them for some time.
A structural instability in the fort's outer wall due to iron-stripping causes a collapse that kills many. As a result, the Knights start 'watering' down the iron rations for the serfs while saying nothing and hoping they don't notice. They notice but with own shells in lesser and lesser conditons, it seems there is nothing that they can do. During this time, several Knight leaders discover the spirit war is long over and they can now return to the plains. They keep this knowledge a secret, not wanting to relinquish the personal power that ruling over the confined keep has given them.
The Spur Clan continues to grow, constructing a rudimentary road through the marsh and linking the Spur to the Plateau. Most of the Plateau spirits are still recalcitrant but can do nothing on their own, prompting them to link up and reclassify themselves, merging into the greater spirit of the Plateau itself. This massive spirit, great serpent with a head of chromium and a body studded with crystal, hurls the entire chromium cap at the Spur, crushing most of the mountain and destroying the vast bulk of the Spur Clan. With most of them dead or dying in collapsing underground tunnels, what little is left of the Spur Clan has to flee into the marsh and eke out rudimentary lives with what spirits they can. There may be survivors but the Spur Clan itself is gone.
The Spear Clan continues to shrink as their refusal to stop strip-mining and their refusal to stop attacking steel spirits leads to the Steel War continuing. And there is an endless amount of steel spirits and only so much Spear Clan. In the end the steel-shell nobility, having had a conspiracy to mutiny linger in their core for generations, flourishing and growing until most of them secretly applied to its ideology, choose to betray both the Chieftain and the underclasses by opening the doors to many domes and forts, allowing the steel-spirits in. The Spear Clan, or the main body of it, dies that day and the untouched steelshells pay homage to the murderous spirits, name them their new benefactors and declare that they are now in charge. This tiny sliver of Lek-kego ruling over the ruins of the dead Spear Clan call themselves the Steel Clan and institute new laws of metallurgical purity. Only Lek-kego with a significant percentage of steel in their shells are proper Lek-kego. Meanwhile the colony continues to exist on the other side of the beach. They are united against adversity and, since they still call themselves the Spear Clan and idolize its traditions, are the only Spear Clan left.
The Knights continue their rations, with many of the lesser Knights now receiving diluted iron as well. Much of the keep has been replaced by lesser materials. There have been no newborns in the keep for an exceedingly long time, for generations if that term applied any longer. What sets everything off are many Knights starting to kill and eat serfs for their iron content, sparking a revolt. The serfs are unable to slay all of the Knights but they are able to escape, the rebellion setting off out of the keep and into other parts of the island so that they can stay close to the Lake. They call themselves the Free Clan. Some of the Knights defect and join them but most of them remain in the Keep, to wait out the passage of time without iron. In the end both the Knights and the Free Clan are doomed to death now, the Knights rotting atop their tungsten treasures with no iron left save what is left in the cracking walls of their own keep. The knowledge of where the other few iron veins in the Shard are have long since been lost, swept away in the war and paranoia and the Free Clan is also doomed to die slowly of crumbling shells and moulting bodies. There seems to be only darkness ahead of them now.
