Antidermis was the essence of the Makuta.
Over time, the Makuta's Antidermis evolved into a gaseous state that didn't need a body. Bitil was the first one to realize this change. Chirox studied some of Kojol's Antidermis to see what had happened and confirmed this.
After Takanuva defeated Teridax in Mangaia, Teridax's antidermis was bodiless, and needed to find a body soon, or else he would disappear. When six Piraka raided Mangaia, Teridax influenced them to find the Kanohi Ignika, which was on Voya Nui. They all wondered how they thought of that, but their leader Zaktan also gained knowledge of the mysterious "Antidermis virus" and how to collect and use it.
When the Piraka first came to Voya Nui, they gained the Matoran’s trust by pretending to be Toa. When suspicions arose, they decided to bring in a test-subject, a Ta-Matoran named Dezalk, to test an antidermis-filled Zamor Sphere on. Immediately after he was hit with the Zamor Sphere, the Matoran became completely dependent upon the Piraka’s orders. The Piraka then told Dezalk to tell his fellow Matoran to gather in the Matoran village, which Dezalk carried out unquestioningly. The Piraka attacked the Matoran village in the middle of the night and fired Zamor Spheres filled with antidermis at all of the Matoran there. Only the six Matoran of the resistance escaped this fate, as they decided not to trust the new "Toa". All of the other Matoran, however, became slaves of the Piraka, losing their own will and becoming entirely dependent on the orders that the Piraka gave them, even to the point of death. This allowed the Piraka to have the Matoran labor ceaselessly and without question, digging at the sides of Mount Valmai.
The Piraka's leader, Zaktan, was the only one of the group able to approach the vat without feeling nauseated or weak, he was also the only Piraka who knew that the virus was actually Makuta Teridax. Zaktan was thus the only one able to fill Zamor Spheres with Antidermis, which he gave to the other Piraka to use at their liking. The other Piraka have noticed that Zaktan sometimes talked to the vat quietly when he was alone, and did not enjoy being disturbed when doing so. When the Toa Inika arrived on Voya Nui, they had hit a number of the Matoran with Zamor spheres of their own which were filled with energized protodermis, thereby freeing them from the Piraka's control. After a fight between the Piraka and the Toa Inika at the Piraka Stronghold, Toa Kongu probed into the vat with his Kanohi Suletu, and discovered that the substance was alive and actually evil.
Later, in a battle between Brutaka and Axonn near the vat, Axonn threw his axe at the vat, and destroyed it, letting all of the virus escape. The essense then floated down The Cord, to the Pit, where Teridax then took over a Maxilos Robot. After the Battle for the Ignika, the Maxilos Robot was destroyed and Teridax had to find a new body. It is unknown how he got into the chamber under the Coliseum in Metru Nui to take over Mata Nui.
At some point, Brutaka was forced into the Makuta pool. He absorbed some of the Antidermis and began stating himself as the essence of the Makuta species. He also began calling himself "we" and knew things the Makuta didn't, but were supposed to, like Spherus Magna, the Shattering, and Mata Nui's body and destiny. His armor also had cracked in several places because of the enlarged muscle and he gained Makuta powers.
Antidermis seems to have different effects on different beings. Matoran infected with the virus become mindless slaves, blindly obeying any command given to them; this applies also to Toa and Turaga. The Toa Inika, however, were exceptions to this, as their lightning-charged bodies counteracted the virus. The cure for Antidermis in this case is Energized Protodermis. When an infected Matoran is hit then the virus is destroyed, but the Antidermis-infected Matoran is not because the virus is blocking them from achieving their destiny.
Brutaka, however, reacted quite differently to Antidermis; when his body absorbed the virus he became stronger, angrier, and more aggressive. As stated above, he also began to refer to himself in the first tense plural "we" and gained knowledge of things such as Spherus Magna and Mata Nui.
Axonn on the other hand was impervious and the Antidermis had no known effects on him.