Kryonian

A long-lived and headstrong race of beings whose bodies are made primarily from ice.

Kryonians can range from being very short to being very tall, and this is something that they can exert at least some control over.

Kryonians generally are very hefty even if they do not appear so, as their bodies are very dense.

There is an extreme amount of physical variance among Kryonians. Off-world, they tend to take shapes similar to the races that designed the fixtures and structures around them.

Kryonians tend to be stout and sturdy, as a healthy Kryonian is demonstrably so via the accretion of more and more ice.

It can't exactly be called "skin," but Kryonians typically come in shades of blue and white. This is variable based on the conditions and elements present where their outer ice layer was formed.

The main Kryonian weakness is to extreme temperatures. While their biochemistry allows them to remain solid and unharmed in a wide spectrum of temperatures, even well above freezing, however above a certain threshold they can no longer maintain their solid forms.

Due to their composition, Kryonians have very durable bodies. When damaged, they are capable of re-growing their limbs and extremities with ease. Even their nucleus, which is responsible for their operation and their sentient presence, is very resilient provided it is kept relatively cold.