LoS vs What you can 'see'

[Daedalus]

Is there a difference here? For some reason I'm getting confused. Say all the heroes are in a room with a few monsters. Say the wizard is right behind the barb and therefore doesn't have LoS to any monsters in order to cast a spell. Does this also mean that he can't see any of the monsters as well?

Anderas answered concisely. I can offer a cited (but lengthy) explanation. I'll limit things to the rules set your familiar with, the North American Instruction Booklet. Hopefully, it will further clarify LoS and what a Hero can 'see' as well as some other applicable terms.

Is there a difference between LoS vs. what you can 'see'? The short answer is no. The definition is found on p.15 under Action 2–Cast A Spell
(Elf and Wizard Only):

“SEE”
For the Elf or Wizard to cast a spell, the target must be visible. Heroes and monsters are only visible if an unobstructed straight line can be traced from the spellcaster to the target.

The term visible here refers to what a Hero can see as a target, but it is also used elsewhere concerning monsters and searches. In the case of a Wizard casting a spell, visible means it can be locked on target. This doesn't mean the Wizard isn't aware of a non-visible monster in a room (see more below.)

There is more to add if your Wizard-in-the-room example is to be fully addressed. That information is found on p.13 under Looking And Opening Doors:

As a Hero, while moving, you may “look” down a corridor or through an open door. Looking gives you the opportunity to see what is directly within your line of sight, such as closed doors, blocked square spaces and monsters. Looking is NOT one of the 6 actions. . . . Opening a door is also NOT one of the 6 actions. Both “looking” and “opening doors” are simply considered to be additional things you may do on your turn.

The terms "look" and "opening doors" are distinct, though parallel activities. "Look" is again defined and even references "see" just down the page under How Zargon Reacts To Hero Movement:

. . . When a Hero “looks” down a corridor, place on the gameboard any closed doors, blocked square tiles and monsters that are directly within the Hero’s line of sight. (See page 15 “SEE” for clear line of sight.) When a Hero opens a door, place on the game-board the monsters, treasure chests, and any other items that belong in that room.

Quoting matters, as it indicates specific rules are in force. When a Hero "looks" he only "SEES" visible monsters in LoS. When a Hero "opens a door," all the contents of a room are placed, including monsters.

Those monsters are seen (not as a quoted term) by the players and their Heroes. From A GLIMPSE INTO THE WORLD OF HEROQUEST on p.11:

As you look down corridors and into rooms, . . . I will place these items on the gameboard for you to see. . . .

Shifting glimpses or partial views are enough to convey that kind of information to back-line Heroes, such as a Wizard behind a Barbarian. From there, it is up to either Hero to reposition himself so that the Wizard can "see" rather than just see a blocked monster.

[mitchiemasha]

See the problem here was Americans wanted to rewrite the rules thinking they were fixing issues of the original. Only they didn't realise they were making them worse.

[Daedalus]

I agree some of the NA rules contain flaws, but I wouldn't go so far as to attribute the entire attempt of fixing EU problems as creating something worse. Something more challenging that necessitates cooperation--that's how I'd put it.

The "see"/see issue mentioned in the OP still applies to both the NA and EU rules in regards to corridors. When the NA Instruction Booklet dropped "Miniatures in the same room are always visible," it differentiated itself by setting the same line-of-sight requirement equally throughout the map.

This both simplifies the rules by dropping an exception while requiring greater tactical play utilizing the main feature of a Quest, the monsters in their rooms. For example, this change better equips Zargon when trying to keep a spell-casting monster alive long enough to be effective. Conversely, the Heroes can better protect low MP or BP Heroes from Zargon's Sorcerers. That's a plus, in my opinion.

[mitchiemasha]

I could of worded my comment better. The 'thinking' and 'issues with the original' was meant as they weren't actually issues in the first place.

[The Admiral]

Fire Of Wrath and Genie are anywhere on the board as well in the EU rules. I don't know why they changed that either although those are spell specific rather than a general rule change.

They also made Fire Of Wrath and Ball Of Flame twice as easy to defend against (unless it's actually supposed to be either shield defends against them in the EU rules, still not sure about that), the non-healing sets needed a buff if anything. US Fire Of Mild Irritation is just a weak Ball Of Flame.

Yeah, I play them with EU rules. I like the EU rule regarding spell casting in rooms, but I can see the logic of actually having to see your target, as you do with ranged weapons. I'll have a good think about that one, as I am happy to mix and match to suit.