The first Embed depends mainly on the demon's Incarnation. Most of the time, it acts as a catalyst, his reason for Falling, or is tied in some way to his Agenda. A Guardian Inquisitor who wants to entice people to protect themselves, perhaps by causing adversity, might have Bystander Effect as her First Key. A Messenger Tempter who believes in Sartre’s adage that Hell is other people might have Everybody Knows or Tower of Babel. This Embed acts as a Key for further understanding of the Descent.
Every time a demon learns a new Key, she also gains a new, unique power, bridging her Key Embeds —an Interlock. This power is usually a way to use the Key Embeds she has already learned together, creating a more powerful, but generally more specific, ability. The Storyteller should consider the Keys being combined, their systems, and the literal and conceptual underpinnings of the Embeds involved and design the Interlocks. These powers are not Embeds, and so can involve Aether expenditures and non-Finesse Attributes. However, they aren’t Exploits, either, and so don’t necessarily endanger Cover with every use.