Context: From the fifth century to the thirteenth, Śrauta sacrifices declined, and initiatory traditions of Buddhism, Jainism or more commonly Shaivism, Vaishnavism and Shaktism expanded in royal courts. This period produced some of India's finest art, considered the epitome of classical development, and the development of the main spiritual and philosophical systems which continued to be in Hinduism, Buddhism and Jainism. Emperor Harsha of Kannauj succeeded in reuniting northern India during his reign in the 7th century, after the collapse of the Gupta dynasty. His empire collapsed after his death.

Question: What declined from the 5th to the 13th centuries
Answer: Śrauta sacrifices

Question: What philosophical traditions developed during the period of the 5th to the 13th centuries?
Answer: Hinduism, Buddhism and Jainism

Question: In what century was Harsha's rule? 
Answer: 7th century

Question: What happened to Harsha's empire after his death?
Answer: collapsed

Question: What area did Harsha unite during his reign?
Answer: northern India