The Host was the name by which Zil referred to the living planet which Blake visited in the aftermath of Gan's death. It was initially believed to be a simple planet by everyone including Zen and Orac, with Blake able to teleport to the surface without immediate problem. It was eventually discovered to be a lifeform that closely resembled a planet.
The Host was referred to by Zil as having no "waking", indicating a lack of sentience. Nevertheless, it had some awareness of the life that inhabited its surface, which it treated as parasites, absorbing its land masses and coating them in saliva pools the size of oceans in order to wipe them out. Zil was killed after falling into one of the cracks in the Host's skin. Blake nearly suffered the same fate but was teleported aboard the Liberator in time. (B: Trial)