The strength of the Leviathan manifests in its Malchut level in the river Gihon. His powers also move the other rivers and then he went back to its source for tranquility in the concealed Light.
The Light that was revealed in Malchut with the river Gihon, went back to Binah of the upper three sefirot, leaving Malchut in darkness.
This action during the Creation process caused the separation between the upper Sefirot of light and Malchut as we read in Genesis 1:4
“וַיַּרְא אֱלֹהִים אֶת-הָאוֹר, כִּי-טוֹב; וַיַּבְדֵּל אֱלֹהִים, בֵּין הָאוֹר וּבֵין הַחֹשֶׁךְ.”
“And God saw that the light was good. And God separated the light from the darkness”
The aspect of removing the Light from Malchut repeated itself on all the levels above. Every level have its own 10 sefirot. When the vessel of Malchut stays without Light it creates desire for the light that went concealed to come back. This is the drive that we experience with every desire that we have.
Daily Zohar # 2638 – Bo – And God separated the light from the darkness