Naruto Shipudden - Bijuu

The Tailed Beasts (尾獣, Bijū) are nine titanic behemoths that serve to drive the plot of the Naruto series. They are differentiated by the number of tails they have, ranging from one to nine. The tailed beasts are living forms of chakra, sometimes referred to as "Chakra Monsters" (チャクラのバケモノ, Chakura no Bakemono), giving them power that far outmatches most shinobi. The tailed beasts' chakra is coloured red. (Naruto Wikia)