So a few questions on how you guys play it.

[Maurice76]

I see no harm in letting players know the stats of generic monsters, as they encounter them often enough. When special monsters are encountered, I see no harm in revealing their stats then and there (so not right from the start, but only once they're face to face with it). I will not reveal what spells a monster may have, perhaps only the number of spells.

[Jalapenotrellis]

So reveal stats but not how many or which spells?

[wallydubbs]

Although Zargon (Morcar) gets the final say in all matters, he should adhere to his own rules. So when a special monster or villain is put on the board the heroes can be told his stats to be sure Zargon will play by his own rules.

When Zargon plays a chaos spell card, he lays it out so the heroes can read the effect. He's not going to play a spell card he doesn't have (otherwise, how do the heroes know he's not just making stuff up?)

Zargon has to play by his own rules too so the heroes can be sure he's playing fairly.

[Maurice76]

Fully agree with Wallydubbs .

Indeed, revealing the Spell when it's cast by the monster is something I neglected to mention. Players must be able to verify that Zargon / Morcar is playing by the rules.

[Daedalus]

Are you supposed to let the heroes know of a monster's stats and spells or not? That has never been clear to me. in some cases it would seem unfair to let them know that the monster has an escape spell, for example. However they are also given the stats of most other monsters in the game. Do you let them know of the number of spells and what they do? Or only one they are revealed?

There is some guidance in the NA rules for not revealing the stats and spells of a special monster from the Quest Notes:

Important: The role of Zargon is a vital one. He serves as the Game Master; . . . he alone has access to the Quest Book.

Quest Notes
. . Read the notes silently to yourself. Important: You will later disclose the Quest Notes information to the Heroes as the Quest unfolds . . .

Using the first special monster, the Guardian of Felmarg's Tomb of Quest 1 as an example, Zargon should reveal this Mummy's four Attack Dice when it attacks--not before--as the Quest unfolds. The same concept applies to spells; they are revealed when cast.

In contrast, the stats of the Game System monsters is clearly identified as information open to all the players. Monster Cards and.Mercenary Cards of the expansions follow the same procedure:

Monsters Cards
Spread out the 8 Monster Cards and put them faceup near the gameboard so that the Hero players can easily refer to them.. . .

Not so for the EU game, however. All monster information must be discovered by the player characters during Quests:

Setting up the Game
. . . The monster cards should be kept, face-up, behind the screen.

Monster cards
These cards are used by the evil wizard player.. . .

[The Admiral]

This is how I play:

Monsters' stats with a card i.e. standard monsters such as goblins, Beastmen, orc archers etc. are always known to the Heroes. The Heroes live and adventure in the world of the monsters. They know what to expect from an orc, chaos Dwarf.

Nothing is revealed about Special monsters. And I mean nothing. Not even if they have any spells, although that can often be deduced from context and/or figure.

[Kurgan]

When we played, the Heroes always asked and Zargon always told (sometimes now we keep stats a secret). It was like in video games where you see the bad guy's lifebar. At the very minimum the Heroes have the monster cards to look at and yes they would see the Chaos spells when they are played.

I personally thinking telling the Heroes the enemy abilities usually increases the tension.