In the face of intensifying global land grabbing and liberalized development, this article provides new empirical evidence on how customary land serves as the ultimate ontological defense for indigenous sovereignty. By analyzing the Ende Lio community, we argue that resilience is not merely an adaptive capacity but a profound assertion of territorial rights that challenges modern market-driven logic through sacred and communal land relations. This research aims to determine the meaning of customary lands, especially as an ontological foundation and as customary territorial sovereignty, to ensure the welfare and sustainability of the Ende Lio indigenous people. This qualitative study uses an ethnographic approach, involving the indigenous peoples of Wologai and Saga as representatives of indigenous peoples in the Ende Lio area, Ende Regency. Data collection methods include in-depth interviews, Focus Group Discussions (FGDs), field observations, and documentation. This research identifies four key aspects that constitute the meaning of Ende Lio customary land: symbols of identity and existence; sovereignty and welfare; sacred space; and unifying factors among indigenous peoples. These aspects influence indigenous peoples to protect customary lands consistently, often even rejecting development that violates customary values. This article recommends the importance of development policies in customary territories that are more responsive to traditions of conservation and management of customary lands.