Nightmare Creature

Nightmare Creatures were created by the Cynrog from the minds of children. A fisherman named Carl Tucker was killed by a hook-clawed one. The Tenth Doctor and Rose Tyler also encountered several varieties of Nightmare Creatures, such as a tentacled one and a centipede. The Doctor and a few others found them garish-coloured and a bit puzzling. They were nocturnal. (NSA: The Nightmare of Black Island)