What can I spend Prestige on?

Solution 1:

The main purpose of Prestige is to add to your Dynasty Score: this shows how powerful and successful your dynasty is. If your final Dynasty Score is higher than your buddy's Dynasty Score, you're a better ruler than him. You are usually going to get a lot more Prestige than you can spend over the course of a ruler's life.

That said, there are a few things you can spend Prestige on, though none of them are particularly expensive, unless you're a new ruler of a young dynasty or otherwise poor in prestige:

1. Creating an Antipope costs 500 prestige.
2. Marrying one of your kids to someone of lower rank than your kid reduces your kid's prestige; it costs -100 prestige per difference in rank. Marrying a commoner with awesome skills can be worth it, but those skills had better be good!
3. Fabricating a claim costs around 150 prestige, in addition to the gold required to bribe the locals to "remember" some facts about your claim.
4. A White Peace (if you're the aggressor) or surrendering a war will cost you some prestige, but you don't need to have prestige in those cases.

Though it's not an action, remember that you get an opinion bonus of +1 per 100 prestige, that applies to everyone. It caps at +20, but it's still quite useful!