This paper examines the significance of the Sŏkkuram Grotto within East Asian Buddhist sculpture, focusing on the iconographic synergy between the “earth-touching mudra” (bhūmisparśa mudrā) and the eleven-headed Avalokiteśvara. I argue that their combined placement forms a central axis reflecting eighth-century “national protection” ideologies shared across Tang China, Silla Korea, and Nara Japan. Section 1 traces the transplantation of the Vajrāsana Buddha from Bodh Gaya to East Asia. It confirms that this imagery evolved to represent the Buddha’s eternal nature, transcending historical biography to embody a sovereign, cosmic authority. Section 2 proposes a novel link between the bhūmisparśa mudrā on the Nigatsudō halo (Tōdai-ji) and esoteric texts like the Mahāvairocana Sūtra. I posit that this iconography represents enlightenment at the summit of the Form Realm (Akaniṣṭha), situating the grotto’s main image at the highest cosmic plane. Section 3 analyzes the sculptural evolution of the Eleven-Headed Avalokiteśvara’s head ornaments. I suggest the transition toward wrathful expressions (fanged faces) reflects a ritual emphasis on the “purity of the three karmas” (sāngō 三業) required of worshippers in state-sponsored ceremonies. In conclusion, the paper identifies a common spatial logic in the geographical placement of these statues. Positioned at strategic “boundaries” or sites with “spring water,” these sculptures functioned as spiritual fortifications designed to purge national calamities and safeguard the sovereign domain. This cross-regional study reveals a sophisticated, shared “architecture of response” in early East Asian Buddhism.