Trisolaran

Trisolarans are a species native to Trisolaris, the only planet in the Alpha Centauri System. They intend to invade Earth as a substitute for their endangered homeworld, and due to this their civilization as a whole acts as the main antagonist of The Three-Body Problem and its sequels.

Anatomy and Physiology
No Trisolarans are ever seen at any point in the Remembrance of Earth's Past series. Consequently, most of their physical traits, including their size and general appearance, are unknown. However, they are known to have an ability to completely dehydrate their bodies to deal with Trisolaris' chaotic and hostile climate. In this state, they can survive for centuries or more, but cannot think or act. Additionally, it is known that they communicate via patterns of visible light produced directly by their brain as it thinks. This renders speech and thought synonymous for Trisolarans, and they cannot lie to each other.

Additionally, a number of other traits can be inferred. During the run-up to their arrival on Earth, they sought to preserve Earth's cities, implying that they are around the same size as humans. They also intended to inhabit Earth without modifying its atmosphere and biosphere, implying that they can use the same air and food as Earth life forms.

Reproduction and Life Cycle
Trisolarans have two sexes, although it is not clear if these sexes can be defined as male or female. To reproduce, two Trisolarans of opposite sex physically merge together, and then separate into three to five offspring. These offspring share some of their parent's memories and personality traits, and as such do not really go through a "childhood" stage of development. Trisolarans have a lifespan of 70-80 Earth years, not counting time spent in dehydration, although their world's harsh environment and government ensure that they do not generally live this long.

Sophons
Sophons are a type of sentient probe created by Trisolaris, made from single protons. To create a sophon, a proton is "unfolded" into two dimensions and engraved with circuitry that uses the strong interaction rather than electromagnetism. The resulting sophon is self-aware, capable of movement at near light speed, and able to perceive its surroundings on both the macro and micro scale. Each sophon is quantum-entangled with one other sophon, enabling instant communication between Earth and the Trisolaran Fleet. They serve primarily as nigh-omnipresent surveillance devices, and also sabotage particle accelerator experiments in order to hinder humanity's development of physics.

Droplets
Droplets are unmanned, teardrop-shaped probes, and the first Trisolaran spacecraft encountered by humanity. They are made of metal modified with an effect that extends the strong interaction to ranges similar to those of chemical bonds. The resulting substance is perfectly smooth and mirrored. Additionally, it is impossibly hard and durable, allowing a droplet to crash into targets at hundreds of kilometers per second with no harm to itself. Because of this property, droplets are often used as weapons, both against spaceships and ground targets. They are propelled by a "propulsion halo" nearly as hot as the Sun's core, which is most likely propelled by matter-antimatter annihilation.