"Thus the therns are used as the principal means for collecting the wealth and labour that the First Born wrest from them as they need it. Occasionally the First Born themselves make raids upon the outer world. It is then that they capture many females of the royal houses of the red men, and take the newest in battleships and the trained artisans who build them, that they may copy what they cannot create.
"We are a non-productive race, priding ourselves upon our non-productiveness. It is criminal for a First Born to labour or invent. That is the work of the lower orders, who live merely that the First Born may enjoy long lives of luxury and idleness. With us fighting is all that counts; were it not for that there would be more of the First Born than all the creatures of Barsoom could support, for in so far as I know none of us ever dies a natural death. Our females would live for ever but for the fact that we tire of them and remove them to make place for others. Issus alone of all is protected against death. She has lived for countless ages."