Tips for a first time dm?
I have built a little world, and decided to use Mythras because I thought the system would be good for a low fantasy world. I am not too experienced with story telling/gming. My player (it's a 1 on 1 campaign) has decided to play a plague cultist. He rolled up a middle aged nomadic assassin slave, so to make it work I borrowed a concept from Elisabeth Wheatley, and made his character a Khadrahan. A person cursed so that he cannot disobey his master which in this setting is a plague priestess. After he roles up his character we have a session zero, where he stealths into a city poisons a barracks food supply, get's out, poisons some livestock, and dips out of the city.
With hardly any effort, or build up he was able to deal massive amounts of damage to this walled city. Seeing how easily he was able to deal this much damage has left me racking my brain to find ways to introduce drama and stakes. I have no idea what to do, other than to just watch him and his tribe completely wipe out and disease every bastion of civilization. I'd really like to become a good gm, but I feel very out of my depth here.