Cosmic cloud The cosmic cloud was an extragalactic , non - corporeal species , that was an irregular shape , measuring some 800 , 000 kilometer s across , and about 400 , 000 kilometers in depth – or , according to Arex , twice the diameters of Jupiter , Saturn and Neptune together . Composition . The cloud itself was composed of a strange combination of matter and energy , and contained element s that were unknown in Federation periodic table s . In order to survive , the cloud lived on the energy it converted of the matter it consumed . This process involved began with the use of strings , that were composed of a combination of koinoenergy ( almost ambiplasma ) that had an unusually high attractive force to gather matter . It then used blobs of highly charged gas eous antimatter , in much the same way the humanoid body uses macromorphase enzyme s , to break down the matter it engulfed in order to consume it . Encounter with the Federation . In 2269 , this huge cosmic cloud was reported moving into the outer fringe of the Milky Way Galaxy . Starfleet Command sent the to investigate the phenomenon , as nothing like it had ever been seen before . On stardate 5371 . 3 , the " Enterprise " located the cloud in the Pallas 14 system and intended to intercept it near Alondra . However , before it was able to intercept , the cloud engulfed Alondra , and proceeded to break the planet up , consume it , and proceed to change course towards Mantilles . Spock theorized that the creature may perhaps instinctively seek out planets to consume in much the same way an amoeba seeks out food . Not knowing if the creature had any selective ability in its search for matter to consume , he warned that it may also seek out star s to consume as well , and may become a threat to every planet in the galaxy . As the " Enterprise " approached the cloud , the cloud grabbed hold of the starship with its strings and began to engulf it . Captain Kirk ordered that the ship fire full phaser s at the cloud mass ; however , this proved ineffective , as the cloud simply absorbed the phaser ' s energy . The ship was then approached from all directions by a number of the clouds antimatter objects , which began to drain the ship ' s shields . These antimatter objects would eventually be deterred by the use of antimatter charge s . After observing this series of events , Spock determined that this cloud , and its processes , resemble that of a living being . This lead Dr . McCoy to warn that if that is the case , and if the shields do fail , then the antimatter objects surrounding the ship would corrode the hull , and everyone on board would be broken down into " nice digestible particles . " Noting that the blobs perform the same function as teeth , as they break up the larger chunks of matter for digestion . In an attempt to escape the cloud , Kirk intended to head for the second opening discovered at the other end of the cloud , meanwhile hoping that if it does have a stomach , that they can give it enough indigestion to turn away from Mantilles . Upon reaching the central core of the cloud , the " Enterprise " encountered large explosions that violently shake the ship , leading McCoy to liken the region to the small intestine . McCoy noted that the small extrusions growing from the wall appeared to be villi , and based on sensor data , were determined to be composed of antimatter . Initially , Spock likened the behavioral patterns of the cloud to " " a huge bull , grazing here and there , in the pasture of the universe . " " He later reanalyzed that assessment after noticing that the cloud made the seemingly intelligent decision to change course from Alondra to Mantilles , indicating that it had a brain . This was supported by the considerable electrical activity near the entryway at the top of the core . In considering the lives of the inhabitants of Mantilles , Kirk intended to use the photon torpedo es to destroy the brain . Spock and Uhura were given the job of locating target points in the brain , however , once analysis was complete , Spock noted that the size of the cloud ' s brain was so immense , that entire offensive armament of the " Enterprise " could not guarantee its destruction . Kirk then considered using a Vulcan mind touch to contact the cloud . Although Spock could not make direct contact with the cloud , he suggested that it could be done by directing the ship ' s sensors onto the cloud ' s synaptic electric impulses , the input could be transferred through the ship ' s computer , then route it through the universal translator , and the ships audio system . Upon contacting the cloud , Spock explained to it that he within the cloud . The cloud did not understand how another being could be inside it . Spock explained that he was on a starship and that the cloud was endangering many like him on the planets that the cloud consumes . He warned the cloud not to consume Mantilles , and to sense it closely . Spock proceeded to enter the mind of the cloud , and in exchange , the cloud entered Spock ' s body , and after viewing several images from the library computer of Earth , the cloud comprehended what it did and stopped its advance on Mantilles , and was successfully convinced by Spock to return to its origin . ( )