Example Sentences:

Ramayana:  Although Vibhishana joined Rama just before the final war, he soon became an indispensable ally who helped Rama defeat formidable enemies such as Indrajita and Ravana.

Mahabharata:  Although Duryodhana treated Karna as an indispensable ally, he was not sure whether Karna would actually be able to defeat Arjuna.

Bhagavad-gita:  If we study the Bhagavad-gita regularly, it will soon become an indispensable guide to shelter and strengthen us during our life journey.