u/Ill_Island9069

So I have a DnD campaign coming up soon. I was wondering if anyone had ideas to make this more fun and easier to make to make the story more in depth and not boring.

This is what I have so far.
The party starts as a group of people who met due to doing tasks together in a corporation. They do all sorts of jobs and have an agent that gives them jobs. They eventually disbanded and started doing adventures by themselves. The big bad villain is Zembrivoux. He is an adult now, but when he was a child he was… troubled. A problem child. He’s like this because as a child his father was murdered by soldiers. Because of this he HATES soldiers. He starts to take over the land little by little and he meets the party in a different way. How is TBD, but it will be different. He takes over the world with his army of dwarfs.

So i know this question is asked a lot, but i was wondering what i could use to balance. I know about kobold Fight Club, but i want to know how to do it just by using paper. Is there a way to roll, if its nessicary it's 5 people all level 3.

Just wondering what other dm's do to extend their sessions i have a main idea but any help would be great. I will paste the main idea at the bottom.

The party are all people who all meet at a tavern drinking and meeting each other just by being friendly. They all choose to embark on a mission. It starts as just as an adventure, doing quests, dungeons, and things like that. But then they meet an NPC that asks to tag along with the party. This NPC’s name is Zermbivoux. Zembivroux is just a human fighter who used to be a soldier until he was fired because of budget cuts. The party will know very little about Zembivroux. Little do they know he is trying to take over the world. His motive is two main things. His dad was murdered as a child by a group of soldiers. For this reason he despises soldiers and the army. The other reason he wants to take over the world is to get rid of all of the armies and have him be the one to decide wars and him to be the one to control everything so no one will ever feel his pain. The party will slowly get information about what's happening and will start to fight his army and when they least expect it he will strike with his army.

Help With Encounter Creatures And Helping Mend Together Ideas I'm brand new to dm and pretty new to dnd as a whole i was wondering what kind of monsters or creatures or NPC's i could use for combat encounters? I also could use some recomendations for prep and other dm related things. Any help would be great