Total War: Three Kingdom's heroes are super-charged warriors capable of dispatching whole units without breaking a sweat. They're pretty awesome. Next week, they'll properly get to show off their skills in the free Dynasty mode. It's a horde mode where three heroes somehow have to survive a battle against an infinite army.
The horde might have the numbers, but the heroes have their legendary special abilities, which may have saved your skin a few times in the campaign, as well as their superhuman strength. It's very reassuring to see a hero wading into battle, knowing that soon all those pesky soldiers will be tossed up into the air by a whirlwind of destruction.
As you kill enemies, stronger reinforcements will appear, and you'll need to deal with enemy generals every third wave. Your heroes will get stronger, too, earning points that can be spent on new skills.
If the endless waves aren't challenging enough for you, you can always bump up the unit size slider and fight mega-units comprised of 960 warriors. Normal units have 80. While Three Kingdoms is the best optimised of all the Total Wars, you'll probably need a beefy PC to push that slider all the way.
Essentially, it's Total War: Dynasty Warriors, but it also sounds a lot like Dawn of War 2's Last Stand mode, which was released as a standalone game and also featured a trio of heroes fighting an endless horde of enemies. Relic and Creative Assembly are both Sega studios, so maybe there's some cross-pollination going on.
Dynasty mode is due out on August 8.