The lowest Sefira represents our world. A world without light of its own.
The light can be received in a pure process of ‘earning’.
An aspect of the female with desire for the Light.
The image of the sefirot below represents the lowest level of the world of Asiyah, Action, where there is an aspect of physicality, material existence.
On higher spiritual levels Malchut is the lowest sefira that manifests the level below it. Therefore Malchut is also the Keter of the level below it.