A greenhart is a red deer in build, a stag standing as tall at the shoulder as a man’s chest, long-legged and deep in the body. Its coat is a dark russet brown under a thin, soft growth of green moss that covers the back, shoulders, and flanks and thickens along the spine into a short mane; the moss is brightest in the wet months and dulls to olive in a dry summer. The stags' antlers are broad and many-tined and often hung with strands of grey lichen that they do not rub off. Its eyes are dark and large. It moves without a sound on the root-mat and stands among the boles so still that it seems part of the grove. It smells of wet moss and leaf-mould, and its call, rarely heard, is a low, carrying groan in autumn.

They live only in the deep, never-cut groves, among the oldest trees, and nowhere near the forest edge, so that most Humans of the basin side have never seen one and many think them a story. A grove may have a small herd that has lived on its ground for as long as the grove remembers.

They browse leaf, bark, moss, and fallen fruit, and lie up by day in the thickest of the old trees. They do not flee the Wood Elves of their grove, who walk among them, but they vanish at a stranger’s step. Their rut is quiet and their herds small.

The moss on a greenhart is alive and grows with it, and the beast is hidden by it in the green dark of the groves as no other deer is. It sheds its winter coat with the moss on it in spring, and the shed patches root where they fall.

Hinds bear a single calf in early summer, born brown and bare; the moss comes in during its first year. They live longer than common deer, and an old stag’s moss mane is thick enough to carry seedlings.

They give nothing taken: no meat, hide, or antler is ever cut from a greenhart by a grove. Shed antlers found on the root-mat are left where they lie or laid at a grove’s oldest tree. They are harmless, and the danger they carry is to those who hunt them, since a greenhart kill brings the grove’s answer and the next grove’s too.

Wood Elves say the greenharts were shaped by the same green pull that shaped their own oldest lines, and that the two grew into the groves together, which is why the beasts are kin and not game. It is so: the greenharts descend from the same Verdant-marked ancestor field of the deep past as the Elves themselves, a beast line that kept its moss where the Elves' line became a people. Few outside the groves believe it, and many basin scholars call it a grove’s pious story. A greenhart seen at a grove’s edge is taken as a sign that the grove is well, and one seen leaving it as a warning. Basin hunters tell of a lord who took a greenhart’s head and whose forest-edge village was refused the funeral rite for a generation; whether the tale is true or not, edge villages tell it to their young men.