The Calamarain were intelligent, non-corporeallifeforms 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")
In the novelThe Q Continuum, 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. Millennia ago, they 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, Picard comparing the Calamarains' nature to a gaseous version of the Great Link of the Changelings based on reports from Deep Space 9 and making a mental note to try and talk to Odo about it at some future date to compare the experiences.
Their name change 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 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.
However, 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.