Although there was no such thing as eternity in this world, the Tree of Eternity was known for its endless vitality. Even if what everyone saw here was just a Seed of Eternity, it was impossible for it not to contain any trace of life, unless it was already dead.
Although the amount of mana that the seed emitted continuously was still terrifyingly large, everyone could sense that its mana was deteriorating. This meant that the Seed of Eternity was merely emitting its previously accumulated mana, but couldn't generate any new mana now. As such, no matter how powerful its mana was, it would eventually be totally depleted.
The question that puzzled everyone was thus easily answered. No wonder the remaining High Elves didn't use the Seed of Eternity to revive the Tree of Eternity. How could a dead seed grow into a tree?