>WOOP WOOP POTENTIAL STUPID IDEA ALERT WOOP WOOP
Biel Tan hasn't deployed an Avatar of Khaine for neaerly one hundred years. This wouldn't be surprising for a lesser craftworld, or a craftworld that is peacable, but this is Biel Tan. The most well known, influential, and martially famous craftworld. That Khaela Mensha Khaine hasn't made an appearance in a year, much less a near century would provoke suspicion.
However, among the eldar, it's considered a bit of a faux pas to ask about this. The inquisition is another matter entirely though, and they already know the answer.
Biel Tan's avatar has been awake this entire time. Biel Tan summoned the avatar for the ghoul campaign, to help a desperate sword wind against a siege of orks with daemon support. The avatar of war led the survivors, many wounded, to victory against the orks, culminating in the avatar decapitating the bloodthirster Yel'Grazruk shattering the spirit of the enemy. The sword wind rejoiced.
Then they noticed the avatar wasn't gone. It had followed the fleeing enemy, and was killing as many as it could reach. The next day, the avatar was still killing. On the fifteenth day, it ran out of enemies to kill, and came back, planted its sword at the center of the biel tan fortification, and waited.
After the twentieth day, the biel tan forces found themselves very worried indeed. The burning avatar still smoldered, glaring out at the horizon. In the face of their persistent god, finally they attempted to psychically contact the avatar, a hazardous venture for even the most skilled warlock.
After the warlock stopped chanting in a dead language, she managed to sputter out "Khaine waits for his chariot." No one knew what that referred to. But when the autarch ordered the sword wind back to Biel Tan, the avatar followed, marched through the craftworld, and returned to his temple, still burning.
The avatar has sat there since, waiting for his chariot.