It is represented by a tomb stone with an empty grave.
- There is a skull in each mission. In order to collect a skull, you have to complete the optional objective, which is about killing a specific number of an enemy unit type. After doing that, a location on the mini-map will flash shortly - keep an eye on this, as this is where you will find the skull.
- Although there are 17 skulls to obtain, the skulls for the Elite Honor Guard Wraith, and for the Flame Decal Warthog do not count towards the achievement.
- It probably refers to the player collecting skulls, and to collect a skull, normally you have to rob it from a grave.
- This is also a reference to Hamlet by William Shakespeare. A gravedigger dug up Yorick's skull, saying "Alas, poor Yorick! I knew him, Horatio." The name of the achievement references that gravedigger