Mercury and the Halflings:
Most people’s experience of halflings are of jolly and gregarious beings who, despite their odd appearance, are almost universally loved for their good humour and soothing talents.
Halflings, as the name suggests, are half as tall as a baseline human. This is hardly their most obvious visual feature however. They are often portly, with pot bellies and short, thick limbs. They also have an extra set of arms, identical to their top pair, which they keep wrapped around their torsos or under clothing. Halflings are also known for both their talent with first aid and healing, and their knack for repair.
This is because to a halfling, they are the same thing. They are synthetic organisms, with metallic alloys making up a lot of their exterior shell and internal supports. Their soft structures are made of complex polymers and plastics, with the occasionally crystalline feature such as their eyes. Their faces are a simplified version of a baseline human, fully capable of expression and speech. Indeed, no one and nothing likes to gossip as much as a halfling.
Their pot bellies contain a dense stack of advanced polymer batteries and capacitors, charged in direct sunlight by the diaphanous and iridescent wings they deploy from the small hump on their back.
This is the origin of the halflings, and the reason their home is Mercury.
Visitors to Mercury will find one of two things. A quick death, or an alien but pleasant forest.
The trees in this forest are artificial, and their canopies connect in a hexagonal grid to block all light from reaching the forest floor. Visitors will find their paths illuminated by the trees themselves, fairy-like lights marking safe passages through the woods.
Unauthorized travellers will find nothing in most of the forests but the trees, and the halflings. Visitors expecting the jolly halflings they are familiar with will find themselves surprised. These halflings are thin, resembling meter-long stick insects more than anything. They lack the pot bellies, wings, faces, and friendly attitude of their larger kin. They move fast, skittering across the ground and up trees with ease. When not moving, they are almost impossible to see among the synthetic branches, and their wire-like limbs are sharp and strong.
And there are a lot of them. Visitors might find themselves stalked by hundreds without ever realising, and hostile visitors rarely have more than a moment’s terror as the forest writhes before they are torn apart by a tide of needle-limbs.
For all this, visits to Mercury are pleasant enough if done safely, usually with a guide or at one of the known safe areas. The trees do more than merely block direct sunlight, or trap residual heat at night. They actively maintain zones of habitable temperature and air for visitors, and keep the twitchy quicklings calm.
This is because the trees are the final stage of a halfling’s life. Born from seed-like pods on the trees, the young quicklings maintain their parents and scavenge resources to grow, until they eventually have enough matter to develop into their hafling forms. Not all quicklings reach this stage, many preferring to stay as they are. The halfling forms leave Mercury to experience the outside world and to gather the rarer, usually organic materials they need to grow into their tree forms. They are very gregarious, and have an intense curiousity about the places they see and people they meet. For all their happy nature, they are also impulsive and excitable, with their natural resitance to damage often encouarging them to leap first and find out how high on the way down.
Upon returning with the required resources, both already consumed and as supplies, a halfling makes its way to the forest’s edge. There, they bury themselves into the ground, and begin to grow. When fully grown, the new treeling connects to what neighbours it may have on the forest’s edge, linking sides of its hex to theirs. The hexes are mainly reflectors for the spires that grow higher, as well as both data and energy conduits. Halflings never stop being notorious gossips even in their sessile forms.
A treeling will seed only once in its life, and only when all sides of its hex are connected to other trees. It exchanges code with them, cross-checking for errors caused by mutation or radiation, before gestating its only children. The newborn quicklings are fed energy wirelessly from the trees themselves, and the residual power is stored in deep root-capacitors for some unknown purpose.
While it may be apparent that the origin of the halfling race is as a self-replicating solar farm, the Fall introduced enough complications and mutations that it is not known whether they bear any resemblance to their pre-Fall ancestors. Certainly, the oldest treelings remember a time when they were the only ones on Mercury, but none remember a time before the Fall.
There are several forests on Mercury, and several variant cultures as a result. These are referred to as Copses. The Copses also have groves within them that are guarded heavily. These groves can be kilometers across, with a sky made of halfling trees. These groves contain entire biomes found on other planets, little bonsai pocket-worlds tended by the Copse. It is not known exactly why they collect biomes, but the answer might simply be for fun.
The treelings might tell you if you ask, but they get bored sometimes, and are notorious tricksters.