From Halopedia, the Halo wiki
It is worth a total of 25 Gamerpoints.
This achievement is represented by a Death From the Grave medal: a white 8-pointed star with an angry face.
- This isn't an easy medal to achieve if you don't use your grenades often. The simple way to do it would be to stick a mongoose as it's about to splatter you, or stick a player then let them beat you down; spawn and repeat one more time.
- It is easy to get death from the Death from the Grave kills just by simply throwing all of your grenades at your enemy, when your shields go down. It is a random, yet effective tactic in close quarter situations. However, it relies on quick reflexes, and, as it is partly based on luck, the tactic may not work.
- Post Mortem is a Latin term used by forensic scientists which means "after death." This refers to the fact that you made a kill after your death.