`Starting with the most important bit immortality.
the likelyhood of the event happening is slim but increases with age. If you succeed in the event (AKA throw enough money at it and pray) you gain the trait immortal. This makes you immunes to dying from age or disease, but you can still be killed by other means.
Next is the religion.
You need to be pagan in order to do this. The requirements to reform are different for each religion (also each religion comes with their own unique bonus). When you meet the requirements make sure to choose Temporal as your leadership which makes you the permanent head of the religion. (think Islam and Mohammed) You can reform and choose Temporal without the Immortal trait.
BUT
If you are immortal AND the permanent head of your religion you are a god technically speaking.
In my case I want to make a Warmongering Religion with a Bloodthirsty God. Pair that with an immortal character and add the fact you gain personal combat skill every time you sacrifice someone; I would have effectively made a character that would be unkillable outside of assassination (Not like that would be an issue as I'd just invite to court the best spymaster as I expand around the globe)`
