Quoted By:
Seethe: Filled with intense but unexpressed anger
More: Greater amount
Fagmark's: This is a portmanteau of Faggot and Denmark and also expresses that you are owned by them
Discord: Generally means chaos, but I know he means the widely used Chat Application
Slave: Someone who is legal property of another person
So, all together:
Be filled with intense but unexpressed anger to a greater amount, the owned property of Fagmark's Discord server.