Multiple people have asked for clarification on Fortify.
Earth
3 : Fortify - Raise a stone wall. You can use this wall alongside another action to give you the effect of Block. You can only hold one stone wall at a time.
On the action that you use Fortify on, you gain a wall which is represented as the status 'Fortified'. On any other action after you use Fortify, in addition to your normal action you can raise the wall to give you the effect of Block for that action. The wall is then destroyed regardless of whether it blocked something or not.
Sample Actions:
Conjure Earth (Life)
Fortify
Conjure Entropy (Life)
Mutation Field + Block (Fortify)
I hope this clears up any confusion.