The Moving Form
Utsava pratimā (Sanskrit: utsava = festival + pratimā = image) is the technical Āgamic term for what is popularly called utsavar (Tamil) — the consecrated image that participates in festivals and processions. Distinguished from the mūla-bera (the fixed, installed icon in the inner sanctum), the utsava pratimā is designed to be carried, moved, and adorned differently for different occasions.
Consecration
The utsava pratimā is consecrated according to the temple's Āgamic procedure so that Bhagavān's real sānnidhya is worshipped in a form suitable for movement and external service. The processional bimba is ordinarily made of a durable movable material, especially metal. Its material substance should not itself be called śuddha-sattva: like other arcā bimbas, it is made from material available in this world, while Bhagavān graciously accepts it as His divine form and becomes truly present for worship.
Devotional Significance
The utsava pratimā embodies Bhagavān's saulabhya — His willing accessibility. Where the mūlavar represents the Lord's eternal, established presence, the utsavar represents His dynamic reaching-out to devotees. The most beloved divine encounters in Śrī Vaiṣṇava devotional life often happen during the utsavar's procession.