Final answer:
The term for skulls that lost their mana is not given, but they were important for the Dobuans as a source of power from their immediate ancestor until the sources lost potency and were replaced.
Step-by-step explanation:
The term used in class to describe the skulls that lost their mana among the Dobuans is not provided in the materials given. However, based on animist beliefs, it's clear that the Dobuans kept these skulls of their immediate ancestor for their power or mana. Once these sources lost their potency, they were discarded and replaced with new sources believed to hold more mana. This practice highlights the cultural significance of mana and the ancestral veneration within their society. While exact terminology for the state of lost mana is not provided, the concept revolves around the belief in objects being imbued with this spiritual force until it dissipates.