The Ace of Keys represents the initiation of a discovery or a new idea.  It is the fundamental force of curiosity, encompassing the drive to solve a problem that lies before you or to learn more about something you've just encountered.  Seeing this card come up in a reading may suggest that you (or someone relevant to the query) will have a brilliant new thought...or will need to have a brilliant new thought.  It may also reflect a state of aimlessness and frustrated innovation, a need to find the "lock" that matches whatever "key" is contained within your own mind.  One way or another, the Ace of Keys is usually connected to the beginning of a quest or a project. 

The Ace of Masks represents the initiation of a new identity.  It is the fundamental force of both outward expression and inward expression -- the power to say "yes, I can be that person."  Seeing this card come up in a reading may suggest that you (or someone relevant to the query) will be called upon to step into a new role in life: parent, teacher, student, friend, lover, anything that puts a new spin on the process of self-construction.  Of course, that role may not be an easy or a pleasant one.  The Ace of Masks is also an elemental representation of deceit, and seeing it appear should always raise questions as to what is real and what is merely a facade.