Adanhu

Adanhu, wisest of the tree lords, was eldest the three remaining Elders of Athel Loren, and held the gift of prophecy. He, along with Durthu and Coeddil, are what remain of the Elder Treemen.

When Durthu brought the children of Astarielle from Avelorn, Adanhu was greatly displeased that the sanctity of the worldroots had been breached. Eventually, however, he eventually relented. Eldest he was and fearful of change, but so too did he fear that the forest’s survival might have come only by sacrificing the gender and peaceable side of their nature. Unchecked, the spirits of the great forest would become an enemy as dire as that which they had fought, and Durthu’s bargain presented some small hope that such a destiny could be prevented. Though Coeddil railed angrily against the decision, Adanhu agreed that Astarielle’s heirs could remain within the great forest until their homeland was safe once more — provided that they never awakened from their magical sleep whilst within its bounds. 17

During the time of the Sundering, when the Elves began to dwell within the borders of the forest, the wayward children of Ulthuan never heard the harsh words that raged between Adanhu and Coeddil as they argued over their fate. Ultimately, Adanhu’s will prevailed, and the forest now opened up many of its secrets to the Elves, though the Dryads and Treemen took care never to intentionally reveal themselves. 18

It was only when the Elves began to despair, trapped in a war between Greenskins and Dwarfs, that Adanhu finally revealed himself. He pledged that the spirits of the forest would fight alongside them if only the battle was brought before winter came. Emboldened by Adanhu’s words, the Elves prepared their plans anew. In their enthusiasm, they were heedless of the ancient one’s warning that a great sacrifice would be required.

As Adanhu had promised, the Elves did not fight alone. Colossal Treemen strode amongst the Elven lines, and great hosts of Dryads swarmed about the flanks.

Through it all, Adanhu and the other Elders looked on with satisfaction. Under the guardianship of the Elves, the forest was flourishing and its wildness was being kept in check. 19

During the Season of Retribution, only Durthu and Adanhu maintained their sanity, as spirits and Elves fought each other, but they could do nothing in the face of the burgeoning madness. 24 As decades passed, the Elders of the forest could stand by no more. 25

Spring came upon them, but there was no sign of renewal. Indeed, they could feel the forest withering and dying around them, and knew that disaster could only be averted if the taint in Ariel’s soul could be cleansed. With the aid of a young seeress named Naieth, who had herself resisted the madness of those times, they gathered what forces they could and marched on the King’s Glade. There Adanhu tried to reason with Ariel. H e sought to turn the Mage Queen aside from the path she had taken, but she denied him, and saw only an army come to dethrone her. Issuing a great shriek, Ariel summoned the maddened Elves and spirits to her side, and ordered her challengers begone.

Battle then broke out in the heart of Athel Loren, though afterward none could say which side struck the first blow. The tide soon turned against Adanhu and his followers, for they were badly outnumbered. Thus did the Elder resort to a desperate deed. Reaching out to Ariel through their shared connection with the Weave, Adanhu drew the taint from her heart and into his own. Alas, that selfless act was Adanhu’s last — the burden which Ariel had borne those long years was too great for the mighty Elder, and he perished instantly.

All at once, the madness passed from the forest. Elves and spirits awoke as from a nightmare, the cloak of vengeance and spite that had clouded their vision for so long at least melting away like snow in the first days of spring. Ariel saw none of this. Adanhu’s final gift had brought awareness of all the harm she had wrought, of the natural cycles she had put out of balance by selfishness. Weeping, the Mage Queen fled and hid within the Oak of Ages, there to atone for her sins and focus on restoring the harm that she had done. 25

Source

 * Warhammer Armies: Wood Elves (8th Edition) -- pg. 17, 18, 19, 24, 25