Sound creature

The Sound Creature was an entity inhabiting an alternate universe. It was unknown what it exactly was. It's physical form was that of a huge ameoba. It learned very fast and comunicated through rhythm.

History
When the Doctor and Charley Pollard were stranded in an alternate universe, they believed that they heard the TARDIS, which had supposedley been destroyed. However, this was just the Creature manifesting itself for the first time, using the first sound the pair had made in this universe. After further walking, Charley tripped over an alien body, they then heard a very faint "help me!". Charley thought that it was the body, but the Doctor says it's long dead, and it can't be reflexes. The help me!'s continued in a seemingly random pattern, until the Creature released a cacophany that greatly frightened Charley, the Doctor scolded it. After a long silence, the Creature began to repeat the humming that Charley was doing to pass the time. The Creature then bombarded them with random snippets of their conversations and then fired off another cacophany.

The Sound Creature in Ameoba form, later attacked the Doctor, but Charley subdued it. Afterwards, the Doctor and Charley continued their trek through the light. Every once in a while, the creature put on a show with it's "Music". However, it got better and better at putting together pieces. The Creature then visited the Doctor and Charley in another form and it tried to convince them to give it full life by giving up theirs, however they resisted it. With a last Cacophonous scream, the sound faded away and was never heard again. (BFA: Scherzo)