How to Unlock Undying Achievement
Die and resurrect 3 times in one expedition. There are three ways to resurrect. The first one is building the Cemetery in the camp. The second, to place the “Ancestral Crypt” tile. The third is to get a trait called “Omicron’s Technique”, which will grant you the third resurrection.
The easiest way to farm this is to get into the first boss expedition, place down the Ancestral Crypt (with it and the passive resurrection from the camp’s cemetery), and place a bunch of Suburbs to level up fast and get the Omicron’s Technique. Then, just die. Three times.