Plot inconsistency with Helena dialogue

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FuliginCloak wrote:

Helena's dialogue concerning Lorrata, which appears after killing the Weaver, presents a confusing situation. She opens by saying, "The tree that Yeena calls Lorrata is the only thing standing in between Piety and whatever awaits behind that ancient gateway to the northwest...". Helena then goes on to implore us to destroy the tree with the Baleful Gem and the Spike, so that we can try and beat Piety in a race to the Pyramid---but if the tree is the only thing standing in the way of Piety, why would we kill the tree at all? Why not just destroy or hide the spike and gem and leave the way trapped to everyone?