Intelligent bipeds that are slowly evolving sentience.

Surprisingly these cybernetic lifeforms were not formed by hand and later given freedom after developing emotions. These robotics are actually a single celled organism from Dok 972 that have the ability to alter the molten metals that cover the majority of the surface into "cells" and slowly build up a living being that's able to change shape to anything with the same volume, the metal of the planet isn't very good as it's melting point is high. The cell uses the surrounding "cells" to generate enormous amounts of heat to keep the metal in a state that can be molded and used as a body. This heat is undetectable by touch because of the odd insulating property of the metal.

Humanoid reproduction is unknown to the other species, namely because they have yet to understand they are single celled organisms in a molten encasing.

The cell needn't respire, and to reproduce it undergoes a very long mitosis phase that lasts the Humanoids lifetime, the cell's mitosis only replicates the structure and not the organelles meaning the new cell removes the organelles from the parent cell before forcing itself from the Humanoids body to find its own. The old cell dies and fails to produce heat causing the body to freeze and form a statue like structure. 

The newly formed cell leaves the old body because it is unable to replace the exact spot the old cell occupied due to the fact that the old cell is still present.

The Humanoids rarely leave Dok 972, those that do always return by the end of their life cycle to allow the Mitosis completion. In a sense the transfer of organelles from the parent cell is a rebirth/cloning process.