Weese was the Understewart of Harrenhal’s Wailing Tower, and like many servants of the fortress, merely began serving the Lannisters after Lady Shalla of House Whent was forced to surrender Harrenhall to Tywin Lannister’s of House Lannister and his forces.
A cruel understewart, Arya Stark was put under his supervision when she, and survivors of the Nightwatch’s recruits travelling to the Wall (whom she joined to escape Kings Landing following King Joffrey’s rise to power), were captured by House Lannister forces.
An abusive man, it did not take long for his cruelty to earn him a spot on Arya Stark’s “List”. Eventually, choosing to use one of the three “kills” granted to her by Jaqen H’ghar in exchange for saving his life, Weese was quitely executed. He was found with his throat torn, being eaten by his dog.