Besides all the obvious changes, like the new warbands, new weapons, new skills, new experience the new campaign system and so forth, there are some other changes to the core rules of Mordheim.
Armour save modifiers
Strength no longer affects armour saves at all.
Breaking Down Locked Doors
Sometimes the battlefield contains a locked door. In order to get though the locked door, and model may choose to break down the door. In order to break down the door, the model must move to the door, during his move, and roll a strength test. If the test fails, the model stops his movement. If the test is passed, the model may continue his move through the door. If the door was broken down, it cannot be locked again, but it may be closed.
When climbing down and failing, half the strength (rounded up) of the hits.
Death of a Leader
If your leader dies, you will still be able to acquire a new leader. The model with the highest leadership in the warband (you choose in case of ties), is the temporary leader. Whenever you buy a new Leader model for your warband, he becomes the leader, and the temporary leader loses the leader special rule.
The model you charged must be within reach (or almost, roughly ½ an inch away from you) in order to gain the bonuses from a diving charge. You do not gain +1 to hit when performing a diving charge, only the +1 strength bonus.
Doors are terrain piece, and some of them may be locked. A closed door is not a real obstacle, and you can move though it without any problem, but it does block line of sight. A locked doors is a bit more problematic, unless you have a key. If you have a key to the locked door, you may move though it without any test, but you spend 1” of you total movement on unlocking the door. You may lock a door you have the key to by spending 1” of your total move as well. In order to get though a locked door without the key, see Breaking Down Locked Doors above. You may always choose to close a door you just walked though, and it costs you no movement.
Dual weapon fighting
When fighting with 2 or more weapons at the same time, you suffer -1 to your WS.
Moving into combat
You need not to charge in order to get into combat. You can make a normal move and end up in combat. You do not strike first when you do this. You may not end a run move in combat. You may only move into combat with models you could see at the start of your turn, or if you cannot end a climb far enough away from them.
Shooting into to close combat
You may target a shot into any close combat, as long as you can see any of the models involved. Whenever you shooting into a close combat, you do not target any of the models specifically, but rather shoots into the mass and hopes to hit the right target. You get a +1 bonus to hit, as if you targeted a large model, this bonus does not stack with the +1 bonus to hit a large target, even if there is a large target involved the targeted close combat. If you hit, you randomise the hit against any models in the close combat, with an equal chance. A large model counts as 3 normal models for the purpose of randomisation.
You roll for injury when loosing a wound while at 0 wounds only.
Zero Level Characteristic
While most models have a wound value of 0, other values of 0 is rare in Mordheim. If you have 0 in a characteristic it impacts you characters abilities the following ways:
Movement of 0; Means your character can't move at all. If you ever have a model with 0, he is retired from your warband as if he where dead.
Weapon Skill of 0; Means your character cannot defend himself, and have a very hard time attacking other models. In order to hit another model in close combat, he needs to roll a 6, regardless of other modifiers. Other models attacking this model only misses on a roll of 1.
Ballistic Skill of 0; Means your character can't attack with any kind of ranged weapon.
Strength of 0; Treat your character as dead.
Toughness of 0; Treat your character as dead.
Wounds of 0; A very normal state. Wounds of more than 0 is simply a buffer.
Initiative of 0; Treat your character as dead.
Attacks of 0; Your character is unable to attack at all, both in close combat and with ranged weapons.
Leadership of 0 or 1; Means your character automatically fails every leadership test he has to take.