There are immortal beings, of roughly the same intelligence of humans,but being immortal allows them to have more time to learn than us.
-biologically immortal which means not aging but still being able to die when heavily damaged.-
The immortals can decide to give up their immortality through a painful and life risking process, only 2 out of 3 can survive,the others die during the ritual or due to infections.
Is religion strong enough to convince immortals to adopt this habit in their societies? The immortals don't have to feel forced, they have to want to do this life risking ritual in which they lose their immortality and start to age normally and eventually die like terrestrial humans.
Usually humans on earth can do anything for religion, things like killing their family,chopping their limbs,burning themselves alive, eating other people while they are alive or causing the death of hundred innocent children are well accepted among some of the most brutal terrestrial religions and still practiced in modern days in some cultures.
But I have the suspect that all the power of religion comes from the concept of death,life has a short and limited time compared to an endless eternity in heaven. That's why (from my opinion) most religions consider life something meaningless that can be easily sacrificed for a superior good, Even the most well known and famous religion on earth is based entirely on human sacrifice.
This makes me think that if people were naturally immortal, religion would be somehow less powerful and people would not give up their lives this easily. Am I wrong or religion is capable to condition even an immortal being?
Also which religion would or is the most powerful at convincing people of anything?
Not the entire society has to be affected by this religion, like in our world there will be obviously people that simply don't understand religion or that don't believe in anything supernatural.