Pāñcajanya — The Divine Conch of Bhagavān
Pāñcajanya is the sacred conch shell (śaṅkha) held in the upper left hand of Bhagavān Viṣṇu and Kṛṣṇa — one of His four essential divine attributes (āyudhas) alongside the Sudarśana cakra (discus, upper right), the Kaumodakī gadā (mace, lower right), and the Padma (lotus, lower left). The name derives from the demon Śaṅkhāsura (also called Pāñcajana) who was slain by Kṛṣṇa in the depths of the ocean; Kṛṣṇa took the demon's conch as His own. The myth encodes the theology: Bhagavān's victory over the forces of adharma produces the weapon by which He proclaims dharma.
Theologically, Pāñcajanya represents multiple dimensions of Bhagavān's sovereignty: (1) Primordial sound — the conch's resonance embodies the cosmic sound of Oṃ, Bhagavān's own vibration pervading the universe; (2) Proclamation of dharma — in the Bhagavad Gītā (1.15), Kṛṣṇa blows Pāñcajanya at the commencement of the Kurukṣetra battle, announcing the war of righteousness; (3) Purification — the sound of a śaṅkha is considered to purify the environment, ward off negative forces, and sanctify the space of worship; (4) Saulabhya (divine accessibility) — Bhagavān's voice/word reaches all beings through the conch's sound, an image of His universal accessibility.
In the Śrī Vaiṣṇava pañca-saṃskāra rite of initiation, the tāpa ceremony involves branding the devotee with the four sacred marks on the shoulders and arms: the śaṅkha (conch) impression is made on the left arm, the cakra (discus) on the right arm. This branding declares the devotee as belonging to Bhagavān — stamped with His emblems. The Āzhvārs sang frequently of Pāñcajanya: Nammāzhvār's Tiruvāymozhi describes Bhagavān as śaṅkha-cakra-gadāpāṇi (the one holding conch, discus, and mace). In classical iconography, the śaṅkha's spiral form (turning clockwise) represents the direction of auspicious time.