Jarvia is a leader of Carta after Beraht's death. She's a major antagonist in quest Paragon's Kind in Dragon Age: Origins.
In Dwarf Commoner Origin she's Berath's second-in-command. After the Dwarf Commoner protagonist and their friend Leske are captured. She retrives them for Beraht, so he could punish them personally. After they get free and kill Beraht Jarvia takes command. The protagonist leaves to fight Darkspawn and Leske becomes Jarvia's right hand. If the protagonist has different origin, then Leske is still her prisoner.
After King Endrin Aeducan's death Jarvia makes her Carta more active and expands her infulence. Pyral Harrowmont and Bhelen Aeducan ask the game's protagonist to eliminate her. The game protagonist wipes out all her subordinates and hired mercs and then kills Jarvia.