For example performing a penance included years of deep meditation, in a state of isolation from the world. As a result or reward for this penance, a God, usually one from the trinity, would appear and grant a Boon. This was usually in the form of some power in the form of protection against certain creatures, or limited power of immortality etc. Similarly curses too were cast when the rishis or Gods flew into a rage. But in many instances these curses had antidotes, which was usually related to some specific incident in the person's future.
Wars too are a common part of Indian mythology.
The Asuras wanted to conquer the territory of the Devas. Many interesting stories are woven around this theme. The Puras too were composed at this time. From 500 BC to about 100 AD, the age of Buddhism and Jainism put Hinduism in decline. Buddha's doctrine took India by storm.