The Raak

The Raak was a mutated fish created by the Mentors on Thoros Beta to monitor their tidal wave control technology. The Raak took much pride in this, until it regressed into savagery. In 2379, it attacked Peri Brown when she and the Sixth Doctor arrived on Thoros. The Doctor accidentally shot the Raak with a CD phaser, killing it. (TV: Mindwarp)