Toward the end of The Sweet Far Thing, Gemma is told that the Rakshana have kidnapped Tom, and will kill him if she doesn't give them control of the Realms. After she arrives at their hideout, Lord Denby starts trying to bully and threaten her, and she completely snaps. She tells him point-blank that Tom is the only thing keeping them alive, and that if they kill him, there is nothing that will stop her from killing them. She sets the place on fire with her magic (which was an illusion, but they didn't know that). They quickly acquiesce to her demands.
In A Great and Terrible Beauty, Gemma finally decides that she has had enough of Kartik verbally and physically intimidating her and convinces him to back off.