At the core of every craftworld, sealed within a wraithbone shrine and joined to the infinity circuit, sits a smouldering figure upon an iron throne. This is the craftworld's Avatar, a fragment of Kaela Mensha Khaine, the Bloody-Handed God of war whom the Aeldari revere and fear in equal measure. In the myths of that people Khaine was broken into countless burning shards, and it is one such shard that sleeps at the heart of each craftworld, waiting.
The Avatar does not wake of its own accord. To rouse it, the Farseers must enact the grim Ritual of Awakening, choosing an Aspect Warrior to take up the doomed office of the Young King. That warrior assumes the role of Eldanesh, the first and greatest of the Aeldari, who in legend refused to serve Khaine and was slain by the war god's own bloody hand. The Young King is given in sacrifice, and as his soul is consumed the shard stirs and rises, clothing itself in the body of the god made flesh.
What wakes is a thing of terrible aspect, a giant of super-heated iron with a core of molten lava, its surface running with heat and its every step scorching the ground. From the hand it holds forever clenched drips molten metal, an eternal echo of the murder of Eldanesh, and in its grip it bears the Wailing Doom, a weapon that shifts between spear and blade and axe and slays whatever it touches. No mortal armour and few war-engines can withstand its wrath.
The Avatar's presence is felt as much in the soul as upon the field. The Aeldari who fight in its shadow are gripped by a share of Khaine's own fury, their fear burned away and their courage kindled to a white heat, while the enemies of the craftworld feel the cold dread of a god of slaughter turning its gaze upon them. Wherever the Avatar strides, the Aeldari fight with a savagery that belies their usual grace.
That the Aeldari wake such a being at all is a measure of their desperation, for the Avatar is roused only when a craftworld's need is absolute. It is the war god given form, living proof that even a dwindling and sorrowful people still carry a fragment of divine wrath within them, and that when cornered they will loose it upon the galaxy without restraint.