So I’m creating a home brew campaign where basically all of the kingdoms are going to war and I had two ideas on why it’s happening and I want to know which is better 

1. this was my original idea basically there’s a guild of merchants who are very influential and basically manipulate all the kingdoms into going to war for their own agenda.

2. My second idea needs some knowledge of the origin of the world, basically 8 mages came together to create a new world but a fighter got mixed up in it sort of imbuing him into the world making everyone more violent and thats why the wars are happening 

#1 lends itself better to D&D inasmuch as your players have someone to hit.  If people are just naturally more violent, how do they win???

The agenda needs fleshing out though.  You can't just say these merchants are furthering their interests and not know what those interests are.  It will come up.

I have it all planned I just am stuck on my phone for the time being and don’t super enjoy writing it on tiny little screen

Also finding out about either way would be late campaign (it’s gonna be a long ride) and they would be fighting really whoever was against their own characters ideals up u til they found out the cause of it all

I like number 1. They do need a reason for why they cause wars though 

Quote from Jack727 >>

I like number 1. They do need a reason for why they cause wars though 

War is pretty profitable. If the guild is powerful enough, it can control sales of arms and supplies.

Merchants tend not to like wars very much. They prefer stability and reliable trade routes. (Army burns the crops to deny the enemy food. Now the farmer has nothing to sell, and the miller can’t make flour so the baker can’t make bread, for example.) Maybe people who make weapons will do well in a war, but other merchants will have their caravans pillaged, and the king’s soldiers raiding their stores for supplies.

So if you’re going to go with merchant’s guild, there’s got to be a good reason (as jack said). Maybe it’s not really a guild. Either the guild is a front for some other group (and they all know it), or there’s a small cabal within the guild that is pulling the strings. That let’s the players peel back the onion — just when they think they know what’s happening, they find another layer.

As for option 2, while I think the flavor sounds cool, I don’t know how it’s something the PCs can solve or fix. Outside of the classic, find the ancient artifact and perform the ritual to remove the hostility from the universe type of thing. Though that could open up a fun follow up campaign, where some bad guy has found that artifact and plans to crack it open, and the PCs try to stop them.

You might be able to mix both of them, but I'd suggest having some hints that the merchant guild is also working with a criminal guild for some plot reason. Because Xanathar is cool.

Ok so my plan for the guild is that it is run by a beholder who has used the guild as a front to gain trust and build an army, so now he has slowly begun to manipulate kingdoms into war so he can come in and kill everyone else. I came up for this a while ago

As for the second one the fighter is still alive and has roamed the world for centuries seeing what has become of it because of him and the only way to fix it is for him to do by the hands of another adventure with his sword which is hidden away

Quote from Xalthu >>

Merchants tend not to like wars very much. They prefer stability and reliable trade routes. (Army burns the crops to deny the enemy food. Now the farmer has nothing to sell, and the miller can’t make flour so the baker can’t make bread, for example.) Maybe people who make weapons will do well in a war, but other merchants will have their caravans pillaged, and the king’s soldiers raiding their stores for supplies. So the guild keeps one country out of the war and sells food from that country to everyone. And if the merchants start selling directly to the governments, then get soldiers guarding caravans and avoid selling through stores.

 

Quote from Halfastbracegirdle >>

Quote from Xalthu >>

Merchants tend not to like wars very much. They prefer stability and reliable trade routes. (Army burns the crops to deny the enemy food. Now the farmer has nothing to sell, and the miller can’t make flour so the baker can’t make bread, for example.) Maybe people who make weapons will do well in a war, but other merchants will have their caravans pillaged, and the king’s soldiers raiding their stores for supplies. So the guild keeps one country out of the war and sells food from that country to everyone. And if the merchants start selling directly to the governments, then get soldiers guarding caravans and avoid selling through stores.

 

 Or perhaps the merchants deal weapons to all sides of the war.

Or if you want a deep and sinister plot - perhaps it is a combination of the two :) 
E.g. The merchants guild is so powerful that their internal power struggle is spilling over into kingdoms going to war. Behind the scenes, the 8 mages are manipulating the guild to fracture in an attempt to reset the economy of the world (either for the greater good, or for their own interests) 

Quote from overchord >>

Or if you want a deep and sinister plot - perhaps it is a combination of the two :) 
E.g. The merchants guild is so powerful that their internal power struggle is spilling over into kingdoms going to war. Behind the scenes, the 8 mages are manipulating the guild to fracture in an attempt to reset the economy of the world (either for the greater good, or for their own interests) 

 

Bonus points if the Leader of the guild has a chain of office which they wear, which is in fact the way the 8 mages are manipulating them!

Quote from Halfastbracegirdle >>

Quote from Jack727 >>

I like number 1. They do need a reason for why they cause wars though 

War is pretty profitable. If the guild is powerful enough, it can control sales of arms and supplies.

 war can be very profitable - "over there"  whether selling to both sides or just your own - as long as your sources of products aren't being affected  you can make big profits - once evereyone is at everyon'e throat and your sources of products become affected war is very unprofitable and stockpiles run down surprisingly fast.