You travel a world map, visiting cities and encountering parties of enemies and friends! You can fight in the arena for phat lewt, or you can lead npc characters and troops into small scale battles! There's an economic engine allowing you to escort convoys and find your own profitable trade routes! You can run in terror from 80+ groups of enemy soldiers, then attack them with nearby friendly forces! You will fight in deserts, plains, forests and frozen waste! You will shoot, stab and throw deadly weapons into people's heads! You will calmly stand with crossbow raised as a knight charges at you, only to clack him in the face moments before he hits your, sending him flying over your head!
Native is very shallow (no story to speak of, no crafting, etc) but mods add anything you might want, from Napoleonic wars to Japanese-themed battles to a huge arena expansion, full crafting of everything in the game and the Last Days, a huge LOTR-based mod where you fight for any of the five teams and take them to victoly!
EDIT - Holy crap, how could I forget the HORSES! The game supports full mounted combat, from couched lances to deadly sabre drivebys. Experience the hilarity of riding away from melee-armed bandits while shooting them in the face! Feel the terror as someone blindsides you on the left, where your bow cannot bear! Tremble as you charge archers, your shield up around your face, waiting for the deadly thwack of an arrow into your mortal coil! Laugh after a battle as your shield and horse are pincushions with arrows sticking out all over the place!
EDIT2 - there is a problem with the environment shadows option (buildings casting shadows), and once that's turned off version 0.800 is very stable.