There are a total of 8 Obelisk effects. In alphabetical order, they are: Endurance, Force, Fortune, Mastery, Skill, Spirit, Swiftness, and Vitality.
To see which one(s) you are missing, go to the Library, Items tab, Obelisk tab. This will show you which ones you have activated.
Like most of the game, the obelisks are likely randomly generated, so this is a bit luck based. However, this achievement should come naturally if you are detailed and diligent in your exploration.