The gods killed them because they turned into evil wizards. Clearly, the telchines apparently lost one of the titanmachias.
Alternatively, their were nine Telchines, children of Thalassa and Pontus. They had flippers instead of hands and dogs' heads; they were known as fish children.
Research suggests they were the original gods of Rhodes, before the onslaught of the Greek monoculture. In the classical records of the post catastrophe period the Telchines tend to play an important part which link them to myths involving Atlantis. This race of artificers, artists and magicians, connected with the sea at every stage in their history, were entrusted by Rhea with the upbringing of Poseidon, which they accomplished with the aid of Caphiera, the daughter of Oceanus.
Another version says that Rhea accompanied then to Crete from Rhodes, where nine of the Telchines (Nine Muses?), known as the Curetes, were selected to bring up Zeus.
We have the names of twelve of them:
Who were the Telchines?
The only female known was Caphiera, mentioned above, which shows that Oceanus was linked to the Telchines. They were said to have been destroyed by the flood. They were skilled metal workers in brass and iron, and made a trident for Poseidon and a Sickle for Cronos, both ceremonial weapons. They could bring about hailstorms, snow, and rain at will, and produced a mixture of stygian water and sulfur, which killed animals and plants. Their habits has been variously given on most of the islands of the Eastern Mediterranean, but this may perhaps be due to the desire of the Greeks to fit them into their own mythology.