When elves died, they would have themselves buried under the Tree of Life. Their bodies would be decomposed by the Tree of Life and once again become a part of the Tree of Life. All started with the Tree of Life, and all ended with it. It was the circle of life.
The Kingdom of Sylve no longer had the Tree of Life, but the tradition lived on. Every elf would ask their family to bury their body under a special Tree of the Undead after they passed away. This peculiar plant could decompose even the body of an arcanist. And, after a year, beautiful white flowers would blossom on its branches.
Most saints and wizards chose similar paths. Their bodies could be extremely dangerous, even after they had died, and could attract much unwanted attention. Most wizards chose to be cremated or to carry out their funerals in other special ways. No matter if they were a common man or a saint, death was painful and, moreover, a significant ceremony of life.