Shalka

The Shalka were an alien race encountered by the the Doctor. They are made almost entirely out of lava and had no set form. The ones shown were large worm-like creatures with cobra-like frills, but there were also Shalka of different sizes and shapes.

They lived underground, near where lava meets metamorphic rock. They communicated by screaming, and breathed volcanic air; the only exception was Prime, the Shalka leader, who was able to speak and breathe oxygen. They used sound as a weapon and a means of controlling "lower alien creatures" and to accomplish other tasks. (Scream of the Shalka)

Behind the Scenes
As the version of the Doctor who fought the Shalka does not exist in established canon, the Shalka themselves may not, also.