From Crusaderkings

Anything counter-intuitive I need to know?

You must save and reload each time your primary title changes. This means when you go from being a count to being a duke to being a king - but it also applies if you are forced by war to change your primary count or ducal title.

Vassals operate according to game mechanics and not psychology: during a civil war, you are often best advised to let your disloyal vassals go free or force-vassalize them without removing their titles until the worst is over. This keeps your badboy score low and keeps your other vassals from joining in the rebellion.

Many events operate across borders. Land borders are usually self-explanatory, but over seas there are only certain specific trade lanes (usually connecting major ports.) For a map, see here.

How can I change my primary title?

You cannot do this in-game.

To edit your save game, open it in a word processor (like notepad) and make the necessary changes.

The fastest way to do this is

• CTRL+H replace all current instances of the new title tag with XXXX. Then
• CTRL+H replace all instances of your current title tag with the new one. Then
• CTRL+H replace all instances of XXXX with your old title tag.

On the other hand, doing the changes this way will cause other lords to have claims on the wrong title.

Should I buy Deus Vult?

Yes.