Defend: resist an attack made on (someone or something); protect from harm or danger.
Defense: a means of protecting something from attack
Carapace: the hard upper shell of a turtle, crustacean, or arachnid.
Venom: a poisonous substance secreted by animals such as snakes, spiders, and scorpions and typically injected into prey or aggressors by biting or stinging.
Poison: a substance that is capable of causing the illness or death of a living organism when introduced or absorbed.
Predator: an animal that naturally preys on others.
Scute: a thickened horny or bony plate on a turtle's shell or on the back of a crocodile, stegosaurus, etc.
Scale: each of the small, thin horny or bony plates protecting the skin of fish and reptiles, typically overlapping one another.