In the beginning, there were no trees.
There were huge constructions made from the enemies' bones, piles growing towards the sky, and the enemies' jewelry hanging from the ghastly "branches". Days were spent compiling the sacrifice together, to show the gods what the year had brought, what had been achieved. Some bones were already dry and whitish, others still held strands of raw red meat and spread a unique smell through the hall.
Everybody was merry. There was beer and mead and roast, songs and naked limbs. And over all, the bone tree presided, and the gods watched and laughed.