Hello, as I said about to start a bastion based campaign (I am a player) and I need a bit of help on how to use bastions and some suggestions on how to make it. For context, I am playing a somewhat dark death themed paladin, who is protecting a necromancer (my friend also a player) and we plan to have a combined bastion.

P.S. I know that there is no necromancer subclass, he has a build already for it. but any suggestions for my build or the bastion are welcome.

If you don't have access to the Bastion rules in the DMG you will have to do some searching.  My Fighter's Bastion has an Armory, Barracks, Stable and Workshop so far.  The Armory upgrades the soldiers from the Barracks, the Stable earns me a bit of profit and my Workshop can make mundane and minor Magic Items.  

A Paladin might want a Meditation Chamber, or a Sacristy for example.  Tough to tell, it's a long list.

Thanks, do you know any good websites to make up moc bastions and what they could do?

Quote from SteelTotoro >>

Thanks, do you know any good websites to make up moc bastions and what they could do?

 Have you read the bastion section in the DMG? What they can do is pretty well defined, as are the rules for combining them, adding on new things, costs, etc.

Actually, no.  I have the DMG to pull from.

Start with the DMG and go over that fully trying some ideas.