Ramora eel

From Tardis Wiki, the free Doctor Who reference

The Ramora eels were a type of giant fish native to Coralee. The ramora eels were massive creatures, the size of trains. They lived in the caves of Coralee, feeding on other fish.

Rajiid, Greg and R'tk'tk would release blood nearby a ramora eel cave, causing it to go into a frenzy and impress the tourists. When they were being attacked by the Krill, they led them into a ramora eel cave and released all the blood, making it kill the Krill in its frenzy. (PROSE: Storm Harvest)