Lannister soldier (The Prince of Winterfell)

A Lannister Soldier is an unnamed minor character in the second season. He is played by guest star Ciaran McMahon and only appears in "The Prince of Winterfell"

Background
This solider is worker for House Lannister.

Season 2
He works for the head of House Lannister, Tywin Lannister. While Arya Stark was working- carrying water- he bumped into Arya, making her waste her water.

In the books
In the Song of Ice and Fire novels, he could have been one of the workers, for Tywin, while in Harrenhal.