What is the core spiritual belief behind immersing ashes specifically in Kashi Ganga compared to other holy rivers or places?

The core belief specific to Kashi stems from its identity as Lord Shiva’s city and the place of Moksha:

• Shiva’s Grace: Immersion in the Ganga here is believed to directly invoke Lord Shiva’s grace. The Taraka Mantra whispered by Shiva is thought to liberate the soul instantly, bypassing further karmic cycles or journeys through other realms.
• Ganga’s Ultimate Power: While Ganga is holy everywhere, in Kashi, her power is considered amplified by the sacred geography and Shiva’s presence. She becomes not just a purifier but a direct vehicle to liberation.
• Breaking the Cycle: Unlike other places where immersion might grant peace or higher realms (Swarga), Kashi specifically emphasizes Moksha – the ultimate release from the cycle of birth and death. This is the unique promise of performing the final rites, including Asthi Visarjan, in Varanasi.