One of the many wondrous peoples that poured forth from the rich imagination of the late J. R. R. Tolkien were the Ents. These tree-like creatures, agonizingly slow and covered with mossy bark, nursed themselves on tales of past glory while their numbers dwindled in their isolation. Unable to reproduce themselves or to fathom the evil outside their peaceful forest — and careful to keep to themselves and avoid reacting to provocation of the tree-cutters and forest burners — they assumed they would be given a pass from the upheavals of Middle Earth. But with the sudden arrival of two...