The Princess & The Pig adds the two titular AI opponents, both designed to test out your skills in very different ways. The Pig returns from the original, while the Princess is a new character.
The former is a brigand who likes to tempt players in with apparent weak points, then fill them full of crossbow bolts from heavily defended towers. The Princess prefers to fling money at her problems, attacking the player early on with advanced siege units and mass infantry assaults.
I've not actually got around to playing Stronghold Crusader 2myself, but I quite like the focus on unique AI commanders – too often in RTS games every AI plays pretty much the same. Oh look,the game an eight out of ten. It must be good!
The Princess & The Pig is currently on offer for 33% offuntil March 27.