Scavenger
In Vino Veritas
As he's on the Loyalist side, Tithys would automatically see him as a threat especially since he witnessed the split of the kingdom. Though their relationship also depends on how they could have possibly knew each other before the civil war. I can see Tithys using Sun's expertise in forgery although.
Yea I see that, If Tithys has had his longsword since his days as an executioner it could easily be a magical blade that Sun had forged to ensure that executions went without the need for re-cuts. Also if he stood by the royals then they would have seen a lot of each other since Sun was both a magical advisor and Tutor to the princess. Also if Tithys tried to spy on any of the princesses lessons he would hear nothing through an opening and unless he knocked all he would see would be Sun and the Princess staring at each other