You should also read through the changes to HoN here, since that includes some important core mechanics.

Madness

* A character with a Madness marker cannot cast spells. Enemy units ignore its ZoC and it can no longer control objectives or fulfill scenario victory conditions.

* There are now two types of Madness.

— Instantaneous Madness (titles in red) have an immediate effect upon drawing the marker. The marker is then returned to the bag of Madness

— Lasting Madness (titles in white) have a lasting effect. If drawn in the Supply phase, apply the effect at the beginning of the next Order phase before placing your Orders. If drawn in any other phase, apply its effect immediately even if the unit has already been activated. The effect is reapplied every Order phase as long as the marker is on the unit.

Special Abilities

The bonus from Mythos Fighter (formerly Mythos Hunter) does not cumulate with any other Mythos fighter bonus unless it has the limitation: "This special ability does not apply to alternate firing actions." This is an explicit restriction, not an omission of the previous allowance.

Casting a Spell

* In order to cast a spell, a character must have no Suppressed markers nor Madness markers.

* Under no circumstances can the cost of a spell be less than 1 Suppressed marker.

* When the spell caster is eliminated, all markers related to his spells are removed from the game and their effects stop. Summoned creatures remain on the battlefield but become Uncontrolled Creatures in Aggressive mode.

Action Cards

Some of the cards have been altered as part of the v2.0 update.

Energy Drain (Black Sun)

Spoiler :

Play before casting a spell.

Place an Activation marker on one more more of your units that have not yet activated, situated at 3 spaces or less from a character.

Remove their Order tokens if they had one.

Reduce the spell penalty by 1 Suppressed marker for each unit that received an Activated token.

Fall Back (Black Sun, Deep Ones, Majestic)

Spoiler :

Play after your infantry unit (whether attacking or defending) lost an assault.

Your unit does suffer a hit, but does receive a Suppressed token.

If the unit was deployed, return it to its more mobile side.

The unit must immediately retreat two spaces regardless of their movement value.

If your opponent is the assailant, they must take your place.

Once More (Black Sun)

Spoiler :

Play before casting a spell.

You can cast a spell even if your character received one or more Suppressed tokens.

Apply the spell penalty.

Opportunity Fire (Black Sun, Deep Ones, Majestic)

Spoiler :

Play during the activation of an enemy unit.

If the enemy unit performs a shoot or a move action, one of your units can shoot at it during its movement action or after its shoot action.

Your unit must not have already acted in this Activation Phase.

Put an Activated marker on it, and remove its Order token if it had one.

The enemy unit can finish its movement if it was not eliminated.

Swiftness (Black Sun)

Spoiler :

Play at the beginning of the Order Phase.

You can give an additional Order to a unit situated 3 spaces or less from a character with a clear Line of Sight on it.

Your unit will be activated two times during this turn.

Place 3 Suppressed markers on your character.

Terror (Black Sun, Deep Ones)

Spoiler :

Play at any time.

A unit with a Suppressed marker must immediately make a Terror check against Mythos 3. You can play this card on a Mythos manifestation.