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The Polyphase Avatron was a robotic parrot owned by the Captain, who considered it his only true friend.
The Polyphase Avatron was feared by the crew of Zanak since it killed without mercy. It attacked by engaging a lift-off sequence before flying and killing its target. It would attack anyone who displeased its master. The Captain sent it to attack K9 who destroyed it. The Fourth Doctor returned the broken Avatron to the Captain. (The Pirate Planet)
The Polyphase Avatron was later kept in The Doctor’s TARDIS with other items in a storage room. (Shada)