A day of Brahma is called Kalpa, which is equal to 432 crores of human years. We are now into the 51st Kalpa called Shvetavarahakalpa. These Avataras of Lord Shiva were in the previous Kalpas as follows:
- Sadyojaata : In Shveta Lohita kalpa Lord Shiva took avatara as Sadyojaata from the body of Brahma.
- Vamadeva : In the kalpa called Rakta, Lord Shiva took avatara as Vamadeva and he was red in colour.
- Tatpurusha : This avatara was in the kalpa called Peetavaasa He wears yellow clothes in this avatara.
- Aghora : In the kalpa called Shiva, the avatara of Aghora, black in color took place.
- Ishana : This avatara was in the Vishvaroopa Kalpa.
The five important mantras of Lord Shiva are based on these avataras.
Sadyojaatam prapadyami...., Vamadevaya namo......, Tatpurushaya vidmahe....., Aghorebhyo...., Ishanassarvavidyaanaam....