The Hive, led by Lord Zarak, are the rulers of the planet Nebulos. Living in an underground city, they possess highly developed mental powers which enable them to control machinery with their minds. They use this ability to control a variety of devices on the planet's surface to both maintain the environment of Nebulos, and to enslave its population. However, these abilities came with a price, as their bodies became weakened and useless.
They found a chance to address this shortcoming when groups of Autobots and Decepticons arrived on their planet. After observing that some of the Autobots had joined with a group of rebels to become Headmasters, the Hive captured the Decepticons with their machines. They intended to replicate the process and gain workable bodies in the form of exo-suits made from the robots' heads. However, Cyclonus protested that he would only allow those Decepticons among them who transformed into animals to become Headmasters. The remaining members of the group instead offered the Hive their weapons, and thus were the first Targetmasters created.
Zarak did not participate in either form of binary-bonding. Instead, he used his powers to rebuild the Hive's underground city into Scorponok: a massive fortress capable of interstellar flight, that could also transform into a robotic scorpion and a titanic humanoid robot. Zarak also built himself a transforming exo-suit, allowing him to become the robot's head.
After Scorponok captured Arcee, and with her the Key to the Plasma Energy Chamber, the Hive departed Nebulos with their new partners, and entered into a somewhat uneasy alliance with the Decepticon leader, Galvatron.
The physical appearance of the Hive members is not consistent.
The first glimpse we get of them is during an exposition flashback shown while Gort explains the circumstances on Nebulos to the Autobots. They are seen from behind while seated in chairs, heavily shadowed, with only the backs of their heads visible. They appear to have hair.
The first "live" look at the Hive comes later as they observe the Autobot Headmasters trashing some of their machines. They are again seen from behind while seated in chairs, in even darker shadow than before. Only the figure sitting to Zarak's right clearly appears to have hair, the others have oddly shaped heads that look more like helmets, or the heads of robots.
Later, we see the backs of the seated Hive's heads in silhouette again, this time observing a battle between the Autobots and the Decepticons. Those odd shapes seen previously are not present, as the figures seen have basically smooth and oval shaped heads.
After the Decepticons have been captured and are deposited before the Hive, we get our first real glimpse at the Hive from the front, in full light. It is a very brief glimpse, lacking in detail, but here the Hive appear to be organic beings dressed in Nebulan-style garb. Lord Zarak, despite his supposedly withered body, appears rather heavily muscled.
Shortly thereafter, as the Hive and the Decepticons come to their agreement, save for Zarak and the man seated to his right, the members of the Hive no longer resemble Nebulans. Instead, they appear to be Lithone-style robots. They would continue with this appearance until they had bonded with the Decepticons and gained their exo-suits.
The man who was seated next to Zarak, and did not appear robotic, seems to be Grax. Although when we later see Grax as he reports to Zarak on the completion of modifications to the Decepticon heads and weapons, he is not an exact match for Zarak's right-hand man. His eyebrows and mustache are dark, rather than the previous white, and overall he appears somewhat more slender. However, his clothes do match.