Lord Shiva; Greatest Devotee of Krsna
Shivaratri is the celebration festival for Lord Shiva, one of the three presiding deities of the material world. To manage the material world, Lord Krishna incarnates as three guna avatars, Lord Vishnu, Lord Brahma, and Lord Shiva. Guna means qualities, and each of the deities preside over a specific quality of material nature. Lord Vishnu represents the mode of goodness, Lord Brahma the mode of passion, and Lord Shiva the mode of ignorance or darkness.
Lord Shiva is known as Mahadeva, or the great god or demigod. He is known as the highest demigod because he is a great devotee of Lord Vishnu or Krishna. Lord Shiva is always seen seated in a yoga posture and meditating, for his mind is in deep concentration on the lotus feet of Lord Krishna. Like other demigods, he has been deputed by Lord Krishna to provide material benedictions to those who worship him. Lord Shiva is generally the demigod to go to for people in the mode of ignorance. People in the mode of ignorance usually crave material benedictions and they know that Lord Shiva is very easily pleased, so they go to him to fulfill their desires.