A Cnidarian artefact was left on Earth early in its history. It was left in a watery cave. It lay dormant for thousands of years until it was found in 1978 by a group of university students.

The artefact looked like it was made of stone. It was grey and large, the size of a lectern. It was smooth and had intricate patterns carved on it. It had a five-sided, panelled head and a rounded trunk.

When the students found the artefact, it absorbed their life forces. They brought it to the research facility associated with their university. Unknown to them, their finding of the artefact sent a signal to the Cnidarian home world, which sent Commander Hydra Sowerbii in his ship, the Water Carrier, to conquer Earth.

Commander Hydra communicated with Dr Leech and the Seventh Doctor via a hologram that appeared above the artefact.

When Hyrda was defeated, the ship was sent back to the Cnidarian home world with the artefact on board. (PROSE: The Invertebrates of Doom)

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