I believe it to be a monument to Slannesh. The tree is adorned with hermaphroditic critters with the one on top getting fucked and having a gigantic penis. Oh, and semen.
^LOL! Warhammer for the win!!! Uh...thinking about it, the birth of Slaanesh opens the dimensional hole known as the Eye of Terror... OMFG! YUKKURIS ARE SPAWNS OF CHAOS GODS!!!
Could it be that Anons and Hieda no Akyu are Slaanesh followers? Reference from Wikipedia: "...the devotees of Slaanesh kill their opponents in the most vile and tormenting ways. They capture lots of prisoners who they torture for days after battle to satisfy their dark souls." Replace "opponents" and "prisoners" with Yukkuris.
To be Unclean That is the mark of the Yukkuri To be Impure That is the mark of the Yukkuri To be Abhorred That is the mark of the Yukkuri To be Reviled That is the mark of the Yukkuri To be Hunted That is the mark of the Yukkuri To be Purged That is the fate of the Yukkuri To be Cleansed For that is the fate of all Yukkuris