Another bit of rambling, Rich. Make what you want of it
About the previous experience of Ash with the Ent I would avoid something direct like a fight in the arena, to emphasize the empathic nature of the Elves and of the Ent.
To make a pop reference... Do you remember "V for Vendetta"? The protagonist is in jail, despaired, and she find a way to talk to another prisoner. And the bonding among the two is tragic and moving, especially when one of the two is taken to her death.
Now, think it in M-e's terms: centuries of captivity, at the hand of a dark god, bent on destroying what is beautiful and worthy in the world.
Ash and the Ent sustained each other, and the Necromancer watched all of it, savoring their despair.
How many times they rescued each other from the pit of madness? For how many years the Elf watched her friend slip into despair and lunacy?
And how many times had her singing brought her back in the world?
Because their captor would let her save her friend. To ruin her another time, and another and another...
In the end, Ash lost all her hope, and only prayed for the end for her friend. Death, forgetfulness, anything but coming back yet another time to remember what happened to her, what became of her.
This is "losing any hope".
Can the Heroes find a glimmer of hope in her?