The game‘s second chapter introduces the first half of the crusade management system.
Basically, you get to control additional party markers on the world map independently of your own, each representing an ‘army’. You use these armies to destroy demon units and forts via tactical combat pretty much identical to the King’s Bounty games’. Each army has its own independent movement range (which doesn’t cause time to pass), and it gets refreshed each new day.
So you pretty much want to go exploring/killing demons with your armies first, then follow-up behind them with your main party visiting all the locations they uncovered. The main exception is Leper’s Smile, which is located across the river to the north and can only be uncovered when right on top of it. It’s a nasty area full of swarm enemies that cause the confusion effect which you have to visit in order to progress the storyline. Then after that nasty area the Lost Chapel will eventually pop-up as a second nasty plot-required area where you may not have access to your whole party. For that location you’ll want scrolls of Death Ward and probably Haste if you can’t cast it normally.
After those two locations the actual assault on Drezen is comparatively simple. You’ll want more Death Ward scrolls here, along with some Communal Resist/Protection From Element scrolls (2-3 fire and at least 1 acid) and Bless scrolls (for the Vrock spores). Also be aware that you won’t get the opportunity to loot the outside areas after you defeat the boss in the Command Room, so make sure to bring everything you want to keep/sell into that area.
Overall this chapter is much more freeform than the previous one and the army combat offers an amusing diversion from the hectic mass bloodshed of normal encounters.