Ulthwé - Era Indomitus: The scryers of Ulthwé were masters of foresight, and had read disaster in the stars long before the coming of the Great Rift, or the Dathedian as the Aeldari knew it. Even with all their artifice, these arch-manipulators were unable to allay the doom that was unfolding before them -- only to mitigate its true and terrible potential.Priding themselves on their subtlety, the Ulthwé Aeldari tipped the scales of conflict where they could, aiding the "lesser races" against the forces of Chaos in a hundred different war zones across the Segmentum Obscurus. It was their High Farseer Eldrad Ulthran who was ultimately behind the amassing of the Crystal Seers and the events on the crystal moon of Coheria during the Battle of Port Demesnus in 999.M41 that saw the Aeldari god of the dead Ynnead partially awaken from his slumber.For millennia the Seer Council of Ulthwé had masterminded the defence of the Eye of Terror and its surrounding planets, holding back the tide of Chaos until Abaddon's alliance of Chaos forces in the 13th Black Crusade saw it finally torn apart.But perhaps their greatest coup was ensuring Yvraine and the Ynnari reached the Shrine of Hera in the Ultramarines' fortress-monastery upon Macragge -- first by a grand ritual that saw her borne across time and space from Craftworld Biel-Tan following the Battle of Biel-Tan, and then by force of arms when the Black Legion attempted to stop them.In this they allowed Yvraine to wrench the Primarch Roboute Guilliman back from the brink of death. Upon Macragge during the Ultramar Campaign, the Daughter of Shades used Ynnead's power to give the Primarch a new lease of life, combining Aeldari insight with Adeptus Mechanicus artifice to sustain the Primarch indefinitely.That act saw the Imperium of Man redefined in a new era. With the Primarch given Aeldari aid enough to reach the Imperial Palace upon Terra during the Terran Crusade, and governance of Humanity's realm taken over by the one soul with mental strength and logistical skill enough to hold it together, Humanity was given the wherewithal to hold back the tide of Chaos -- for a time, at least.Though they had done so by methods so indirect that none suspected their intervention, the Seers of Ulthwé had created a Human shield against the scourge of Chaos so broad and so strong it had borne the weight of a hundred invasions and still not shattered.Yet even the finest bulwark will fall apart under the relentless tide, and even Ulthwé was not infallible.The scryers of Ulthwé sifted the visions that entered their minds when they let their consciousnesses drift along the landscape of the future, picking out those fault lines where a concerted attack could shatter their plans.Some of those Imperial planets they watched over were corrupt, their Human masters looking after only their own interests as their cities and people burned around them.On these, the Ulthwéans resorted to that most desperate of all courses of action -- direct intervention. Planetary Governors and their councillors who were too corrupt or slow-witted to stop their people from falling to Chaos were attacked by Black Guardian warhosts and stealthy Aspect Warrior forces who slew the leaders of each failing enterprise.In this, the craftworld ensured its targets' replacement, usually with more competent individuals inspired to proactivity by the shocking demise of their predecessors.The Imperial worlds that Ulthwé attacked found themselves ruled capably once more, each planet a stronger link in a chain that would hold back the tide of Chaos for a little longer.