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. Millennia ago, they were known as the Coulalakritous, but changed their name, perhaps as a 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".
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 of 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.