I like to imagine that one of the ways Cassandra keeps tabs on Cullen in their off hours is by having him teach her chess…and instead of monitoring his behavior she only gets increasingly more pissed off that she isn’t winning.
Cullen: “It appears I once again have you at a material disadvantage, Lady Cassandra.”
Cass: “Bullshit! My tactic was sound. In a battlefield, a proper army could have easily outmaneuvered-”
Cullen: “If you don’t forfeit we’ll be here all night.”
Cass: UGH! *flips the whole board off the table*