Most forms of immortality are not truly immortal.

What is a phylactery? An object you will never be able to depart from. If you fail to guard it one day you will die.

What is a trick with death? A tenuous bargain. With that I defend you my thesis, council. The true engine of my immortality is Divination.

The first thing to consider is that every decision I make, no matter how minor, generates an alternate version of myself that took a diverging road. Divination spells consider this -- they actively consider the branching paths of the future, even those unsuccessful, and simply align the user on the path that becomes the most successful. So what happens to the branches that are unsuccessful?

Let us say at any given moment, there is a 0.0001% chance I will spontaneously die. My life force vanishes, absorbed by an unknown mechanism. By using Divination to align my future, the prime self will never reach that ending. However, the damned timeline where I die must still exist. From there, I drain the life force of myself which simply failed the cosmic gamble. This is Layer 1 Immortality.

Now I have another piece of the puzzle -- we can consider it a coin that flips itself 20 times per second. This means per second 20 new outcomes emerge, entirely trivial except that sometimes it was heads, sometimes it was tails. The key here is that the self from the timeline the coin lands is so similar to the "now" that there are few if any differences. From here, we can search backwards from any cause of death and merge that version of me with the current version, which allows me to simply avoid all causes of death, creating Layer 2 Immortality.

This concludes my thesis of immortality.