I just got heroes of might and magic 4 as i have played it a long time ago and i have a few questions.

1)I want to play chaos as a thief but dont understand how that class works as regarding heroes. Ive played death and might heroes mostly but cant seem to figure out how a thief can be beneficial.

2)Is there a mode or level where your heroes are saved after each level. I dont like having to start a new hero each level or world as i find it to be less roleplayingish. Basically i want my heroes or at least hero to carry over.

Any help is great.

1- Thief has scouting (which allows you to see exact numbers of enemy troops, etc.), pathfinding (removes terrain penalty and adds movement on the adventure map- very useful), stealth (while traveling alone, you can bypass enemy monsters, pick up anything that isn't nailed down, flag mines, whatever) and seamanship (which acts as Tactics, but only in sea combat and also adds movement on sea. Obviously, only useful on map with a lot of water).
Basically the thief is a scout/gatherer/movement enhancer.

2 - that works only in campaigns, because only there it makes sense, I don't see why should it work in scenario maps which don't have anything in common. Also, get some user made campaigns, for example Lamentia's story and Wind of Thorns are great.

In addition to what Klaymen said:

- Scouting: The higher scouting level available in your army, the better you can see around. Every level increases the radius a bit, and you can also see more information about the opposing armies (e.g. number of troops, skills of heroes, artifacts equipped etc). Generally this is a waste of levels, as you can easily send a number of armies with one low-level monster each doing the scouting, and save/load takes care of any unexpected army powers.

- Pathfinding: Very useful skill which increases the movement points of each member of the army by a given percentage. The percentage also stacks with Equestrian Gloves and Boots of the Wayfarer for even higher movement. Also, pathfinding takes care of terrain penalties. It is *very* useful to buy a support thief and invest enough experience to get Grandmaster pathfinding (can be done as quickly as level 6). Likely you will never fight with this hero (as you *need* GM Combat and GM Melee for fighting heroes, too, and that means level15-18 at least, which is quite hard to get), but the movement boost from him can easily win a game.

- Navigation: Acts as a combined Tactics, Offense and Defense, but only for marine combat. It may be useful in some water-heavy maps, but as far as I am concerned, I never enountered one where Navigation would be better than Combat+Melee+Resistance.

- Stealth: This skill pretty much *requires* that your thief wanders alone. It has two effects: one, when approaching an army, you get some skill points for walking around them unseen (this bonus used to be VERY substantial in the first version of the game, but was severely reduced in subsequent patches and is pretty much worthless now). Second, if there is a space around an army, you can often walk around it and gather whatever that army protects, be it a mine, an artifact, a quest hut... As most maps take care NOT to provide enough space to walk around critical armies, it is reduced to gathering artifacts early. For this reason it may make sense to buy an extra Thief and build him to expert Stealth, to be able to walk around level 2 creatures and get their artifacts early, but it is usually too weak a skill to be worth upgrading to Master or Grandmaster. (Note: You need skill level one higher than the highest level of opposing creatures.) This is how the campaigns (official and fan-made both) work.

2) This completely depends on the mission. In the official campaigns, all story-based heroes (i.e. the ones who must survive) transfer. Only Lysander's campaign allows carryover heroes aside from the usual campaign characters. Then again, one could easily mod the campaigns to allow as many carryovers as you wish.