Ood are not monsters. They are a peaceful race, sophisticated and wise, and loyal friends of the Doctor. However, when they are taken over and controlled by evil entities they become monstrous creatures, acting against their instinct with lethal intent!
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, Oodkind often undergo a change of eye colour, so watch out for Ood with red or green eyes!
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.