There are a few ways to earn Mirian fast in Shadow of War. Check out the handy video guide above, created by our friends at GamesRadar. It explains the five easiest ways to earn Mirian in the game, none of which are too tricky to do, plus it offers tips on timings to get the most out of your orc army.
The pointers here include selling loot, tracking down orcs who are guaranteed to drop decent amounts of Mirian, sending your orcs to do battle and more. As you get deeper into the campaign, this guide should help you gather all the resources you need to progress.
If you're right at the start of the game, though, be sure to check out our separate beginner's tips to Shadow of War.