The Calamarain were intelligent, non-corporeal lifeforms that exist as swirls of ionized gas. They were once tormented by Q, who insisted that he did nothing "bizarre" or "grotesque" to them. The Calamarain communicated with high-pitched noises and grindings. They emitted Berthold rays when probing something.
When Q lost his powers in 2366 and was exiled to the USS Enterprise-D to live as a Human, the Calamarain sensed the chance for revenge and attacked Q and the Enterprise. To save the ship, Q took a shuttle to divert the Calamarain's attention away; this noble deed convinced the Q Continuum to restore his powers. Q immediately attempted to exact retribution against the Calamarain, but Q2 forced Q to let the Calamarain go without harm. (TNG: "Deja Q")
The Calamarain returned in the novel The Q Continuum, when they confront the Enterprise-E as it attempts an experiment intended to breach the Galactic barrier. When Q appears to instruct Picard that the barrier should not be breached, he reveals that, millennia ago, the Calamarain were known as the Coulalakritous, existing in a state of continuous debate and discussion that puts Picard in mind of a university when he is briefly converted into a Calamarain by Q to experience their perspective himself. During his time as a Calamarain, Picard compares their nature to a gaseous version of the Great Link of the Changelings based on reports from Deep Space 9, and makes a mental note to try and talk to Odo about it at some future date to compare the experiences.
The name change from Coulalakritous to Calamarain may have been the result of their profoundly negative experiences with 0, a Q-like being who attempted to use them as his personal transport due to his lacking the ability to travel faster-than-light. Their hostility towards Q is due to Q accompanying 0 at that time, having come to regard 0 as a kind of "mentor", although he really did little to the Calamarain themselves apart from accompany 0 and actually objected to 0's attempt to attack them.
While Picard is away, the Calamarain attack the Enterprise, believing that its efforts to breach the barrier are part of an attempt to rescue 0, who was trapped outsider the galaxy by the barrier as part of a punishment by the Q Continuum. During this attack, it is revealed that the Calamarain communicate through a sequence of tachyon emissions, which are translated by Data and Deanna Troi to a limited extent. After 0 manages to escape on board the Enterprise, at the end of the novel, thanks to the pleas of Jean-Luc Picard (and the sacrifice of the USS Enterprise-E's security chief to save them from being compressed into a ball of ice by 0), the Calamarain, if not explicitly forgiving Q, acknowledged that 0 was the greater threat and merged with Q, combining two infinite powers to become more than infinite and giving Q the power to vanquish the insane 0 before the two split once more.