Ood are not monsters. They are a peaceful race, sophisticated and wise, and loyal friends of the Doctor. However there have been instances when they were taken over and controlled by evil entities becoming monstrous creatures, acting against their instinct with lethal intent!
Ood individuals have two brains, communicate with each other using telepathy and although much about them remains a mystery, we have glimpsed their planet and marvelled at its majesty and beauty. The Ood known as Nephew was manipulated by the malevolent House and earlier, on Krop Tor, the Doctor encountered Ood possessed by an evil force that compelled them to attack humanity. When under the influence of others, Ood-kind often undergo a change of eye colour, so watch out for Ood with red or green eyes!