| Category | Forests |
| Continent | Brucrumus |
| Regions | Cinazan, Grashakh, Tribe Steppes |
| Map | Arinthil Forest |
Arinthil is a great temperate forest spanning three regions - Cinazan, Grashakh, and the Tribe Steppes. From the south, it beings at the head of the Shadow Rift and ends far north at the Maranwë Tîwele; the "honey plains". From Tamoroc in the west, the forest is cut by hundreds of game and war paths. Some of these are so rutted that they pass for roads.
Thousands upon thousands of hooves, for centuries driven by blood-lust and plunder. West they go, across Arinthil and into Grashakh and Cinazan. For many, their last great ride. The impassioned say it is a culling of their own, a way to preserve Tamoroc's rich bounty. Don't be fooled, these are Jara, cursed, crazed from heresy, destroyers of anything weaker themselves.
- Cáno, of the "War Spears" in Lúinwë - "Against Safe Passage"
The Jara have been crossing into Arinthil for centuries. Sometimes as part of a massive horde headed by a Jara Khan. The goal is always to raid and plunder, never to hold what they capture. Late in the First Epoch, elves, Forstneblin and Nermaneans settled in this forest. They were quick to join together against the Jara menace.
By the middle of the Second Epoch, Ithengee and Lúinwë forts and bastions, most in the trees, were protecting large areas; and routinely getting the better of the Jara. An unspoken truce came into play, Arinthil's defenders looking the other way as the raiders pass through their lands towards a more dangerous foe. This greater threat is the Orchish Empire. When this empire push northeast in the Core Offensive, seizing new lands and building settlements, it greatly narrowed the frontier between Lúinwë, Ithengee and a much larger empire with a more serious desire than the Jara, conquest.
Over three epochs, Arinthil has been shaped. There are pockets of towering trees improved upon with arcane and nature energy to be resistant to fire and strong enough to hold large forts. Others are simply very tall, serving as watch towers. There are those coaxed by magic to have a multitude of branches and thorns, sharp and hard. The Fograth call them "pork pines". Fograth battle manuals define them as defensive arrays used to funnel attackers into killing zones. The forest also has blocky trees with branches as thick as the great columns of Bor. The frequently used war paths of the forest floor are shadowed above by a networks of vines encouraged to link with other trees, becoming bridges for nimble elven archers.
Arinthil is difficult terrain to travel. It is great for hiding large groups with varying elevations, dense foliage, and cuts with numerous ravines and brooks. There are view areas of open ground. In the forest's northern parts, rivers are the preferred, and safer, route for getting about. Most roads lead to a river settlement or stronghold with canoes, rafts, ferries and possibly sailing ships.
It is customary for Jara to entomb their fallen Khan in very large barrows. Many of these Jara Khan Tombs are hidden among Arinthil's southern hills. The most notable of these is the Mound of Bone Pounder.