Besides, even Epsilons perform indispensable services.
There are no more uses of "indispensable" in the book.
Show samples from other sources
Then a big pot was brought out as we raced to retrieve our indispensable spoons and bowls.
Leon Leyson -- The Boy on the Wooden Box
In fourteen years in Bluffton he had sired two sons and managed to worm his way so completely into Bennington’s life and make himself so indispensable that he sometimes seemed like Bennington’s third leg.