Jessica can use Serpent's Bite after allocating 100 skill points into her whip skill. It deals 160% -> 130% -> 110% -> 80% -> 50% -> 30% damage for 8MP, and has the Strike/Rock element.
Serpent's Bite can be used by any character that has the Working with Whips (quest #74) item in their inventory. It attacks a group of enemies twice with proper Earth damage for 16MP.
Serpent's Bite appears as a combo finisher for Jessica, used when she performs three light attacks in a row, followed by a heavy attack. When used, she creates a jagged pillar of rocks from the ground that will damage any enemies near it.