An offshoot of rebel Quarks would go on to conquer worlds on their own. These Quarks were dangerous enough that the Doctor was forewarned so he could place John and Gillian in a safer location.
Quarks were cuboid in shape with a sphere on top two spikes come from opposite sides of this sphere and one comes out on top. They had rectangular compartments on their chests where their cuboid gun folded inside. The spore spikes were red along with the rim attaching them all. The rest of the sphere is black and the body is grey. The robots' feet were large pieces of metal in the shape of a block; poles attached these to the body.
Dominator Quarks communicated with bleeps,shrill squeaks,and squaks. while the independent ones were capable of speech.
Quarks were able to use their guns to kill directly, stun, electrocute, communicate and to power up objects. They could collect data from a survey just by turning 360 degrees. They emitted warning signals when tripped or covered.
The Dominators had symbols representing each Quark on a wall, the symbol for the corresponding Quark flashes when that Quark was destroyed.
On several occasions, the independent Quarks used Giant Wasps to cover for their limited agility.
Quarks were originally the robot servants of the Near-Human Dominators. The Doctor and his companions first encountered them on Dulkis. Among other tasks, they operated drills for the Dominators.
Other accounts show the Quarks working alone, without reference to the Dominators. They were famed for their brutality and conquests. Jack Harkness referred to "rebel Quarks" in a report on the Vespiform, implying these were Quarks who rebelled against and broke away from their Dominator masters. At some point in their history, these Quarks waged war with the Vespiforms. They appear to have been active at the same time that the Dominators were using Quarks.
The rebel Quarks had multiple battles with the Second Doctor, especially in their attempts to invade Earth. Their first attempt was in 1968, where a Quark spearheard destroyed a radar tracking station in Scotland and made a landing at an old castle. The Doctor seized their ship and used it to take out the invasion fleet. After this encounter, the Quarks were all ordered to search for and kill the Doctor.
At some point, they attacked the planet Gano. When the Doctor and Jamie arrived there, seemingly in 1968 as well, the Quarks unleashed their Giant Wasps. At another time, apparently on contemporary Earth again, the Quarks ambushed the Doctor and buried the TARDIS under rubble in an attempt to prevent him escaping.
In 1971, when the Doctor invented the Martha series of houseworker robots and sold them to an American company, the Quarks waited until they were widespread across the country and then turned them against humanity. This was intended as a prelude to their invasion, but they were routed when the Doctor reprogrammed the Marthas to engage the Quark armies.
In 1984, slave Quarks were part of a Dominator secret invasion of Earth. They came up against UNIT forces under Iceland. UNIT's Major Whitaker ensured their destruction.
In 2044, a Quark squad arrived on the planet Hekton to kill the Doctor, but were defeated by the Human colonists.
In 2053, a Quark assassin pursued the Doctor when he participated in an automobile race on Earth.