The conversation surrounding Shadow of War might be completely dominated by the question of just how much lootboxes and microtransactions affect the experience (which is to say: Not at all), but under the hood there's a remarkably clever, innovative and pretty original game.
Building on Shadow of Mordor's 'Nemesis' system where any random enemy could kill you and rank up in importance (resulting in revenge missions and other face-offs between similarly-powered foes), Shadow of War builds an entire sense of progression around that mechanic. Now you're forever accruing new orcs (recruited in-game or optionally purchased from a vendor named The Headhunter) and pitting them against a series of fortresses in need of taking over.
You can assign spies to get the jump on specific high-ranking Warchiefs once a siege is underway, position your friendly orcs to thin the ranks in general, and even summon in others as active bodyguards during gameplay.
There's a TON to be getting on with - seriously, the amount of menus, stats to track and challenges/loot-drops can be very overwhelming - but if you're walking into Mordor, make sure you know how to make it out the other side.