First of all, sorry for the long post.
Quest 5 “Last Wishes” first time we see Staircases… and we need an explanation:

Now, let’s say that we have 2 areas “Area1” and “Area2” connected each other only by a staircase.

So we have understand that through staircases:
A- Single-target attacks (melee, ranged and magic) works normally, as usual they must follow the line of sight rule (LoS changed to the staircase rules).
B- Breath attacks can’t be made .
C- Explosions in Area1 don’t extend to Area2, radius doesn’t matter.

The questions are the following:
1- If a single-target melee attack is viable trough staircase also Aura effect should works as the 2 staircase are adjacent… right?
So if a master hellhound is in the staircase’s square of Area1 and a hero move to the staircase’s square in Area2, the hero will suffer damage from Aura?
2- May I do BLAST attacks in Area2 even if I’m in Area1, by targeting an empty space for which I have line of sight (respecting staircases line of sight special rules)? Or Blast attacks are considered similar to Breath attacks and this prevents me from doing Blast attack through staircases?
If I can make a single-target magic attack trough staircase I should be able to target a single square from which generate a Blast and then calculate radius (Ok, radius doesn’t extend through different areas)… am I wrong?
3- The 2 end of staircases are considered adjacent for movement and range… but not for some (all?) abilities: exactly what doesn’t pass from Area 1 to Area 2?
Does Command pass through? Someone in Area1 can give bonus to someone in Area2?
Knockback? May I use an attack to throw an enemy form Area 1 to Area 2 using staircases?
Grapple? As the example in question 1 replacing the word Aura with the word Grapple.
Runewitch Astarra has the hero’s abilty “Glyphs activate when she moves within 6 spaces of them” .. staying in Area1 does she activate glyphs in Area2 within 6 spaces from here?
4- Can a hero shoot a blast attack through staircases in a square for which he has LOS in an area that they haven’t explored yet, and then expect to inflict damage to monsters in the blast’s radius even if they aren’t on the map (because heroes haven’t explored it yet)?

RULES ABOUT STAIRCASES and FAQ
Staircases: “..Attacks may be made through a staircase just as if the two staircase spaces were adjacent. A figure standing on one end of a staircase has line of sight to the other end of the staircase and its adjacent spaces, while a figure standing adjacent to one end of a staircase has line of sight to the other end of the staircase.”
Blast:”… A space is only affected by the Blast attack if it has line of sight to the target space.” (and is in Blast’s radius)
Breath (FAQ 3 July 2012):”… Breath attacks cannot be made through staircases.”
(FAQ 3 July 2012):”… The radius of a Blast attack or other area attacks (such as the Word of Vaal, Sweep, etc.) DON’T extend through a staircase.”
(FAQ 3 July 2012):” For range purpose each staircase square count as 1 space.”
(FAQ 3 July 2012):”Q: Do the effects of abilities such as Aura, Spiritwalker, Command, and Kirga's hero ability (from Altar of Despair) extend through staircases?
A: Only non-area of effect attacks may go through staircases.”

Probably all the answers to our questions lay in the last sentence … the problem it isn’t clear to us, maybe my poor English, but exactly what does it mean?
1- Only attacks may go through staircases? So Command doesn’t work because it is an ability and not an attack? Aura is considered and attack or it is not because you don’t roll dices? All the abilities do not work through staircases?
2- And only single-target attack may go through staircases, or also area-attacks may go through staircase? Ok, Breath attacks can’t, and anyway the radius of area attacks don’t extend through staircases, so the explosion is limited to a single area. But is possible to shoot a Blast attack from an Area A to an Area B, through staircases? (always with LoS limitation for staircases)

Again: sorry for the long post.

BerserkOL said:

No. The staircases are not actually adjacent, they just count as adjacent when determining range or movement. Aura requires adjacency (which is different from range 1) so it does not pass between staircases. This is confirmed by the final FAQ answer below.

BerserkOL said:

I don;t think so. Its slightly uncertain because the argument can be made the the Blast attack is the Area of Effect attack not the blast itself, and so by FAQ can't pass through. I tend to think that is just sloppiness on the part of FFG. The blast attack is a single space attack with an AoE affect, so it can pass through, but the effect will not.

BerserkOL said:

Command, no. Its not an attack and not movement.
Knockback, yes. Its movement.
Grapple, no, its not an atack and not movement. It works by adjacency and teh stairs are not actually adjacent.
Astarra, no. Its not an attack and not movement.
Command grapple and Astarra are confirmed not by the final faq answer below.

BerserkOL said:

No. Because the monsters aren't there yet to be damage. Until they are placed on the board, they do not effectively exist.

BerserkOL said:

Its effectively a no. None of those things are attacks, so none of them pas through staircases.

Incidentally, an attack is an attack, defined as such. Aura is not an attack. The use of dice is irrelevent (not that I can think of any attacks that don't use dice).

BerserkOL said:

I think so. Although we routinely call Blast an AoE attack, I don;t believe it is the attack itself that is AoE, just the actual explosion effect. This contrasts with Breath, Bolt, WoV and SS and Sweep, which affect multiple spaces directly, rather than affecting a single space and then having an AoE effect come from that space. (Yes, probably our sloppiness in this is also used by FFG in places).
So I would say you can 'toss' a blast through stairs as it is a single space attack (at least at the time it goes through the stairs.
I think this is backed up by the wording of the second faq answer above, which differentiates the radius of a blast attack and other area of effect attacks.

I'm sure someone will argue differently though.

Knockback won´t work through a staircase because you need to spend 1 MP to move through them and Knockback does not generate MP. A similar ruling would be valid for Magic Portals in an AC.

+1 to all other answers.

Thank you for the answers, I agree with you on about all.

BerserkOL said:

BerserkOL said:

An AoE attack is defined as any attack that affects multiple spaces at once. Blast attacks do not "change" from single-point to AoE at any point in the middle of the attack; they are AoE the entire time by virtue of the Blast keyword being associated with them.

Under a strict reading of the FAQ, Blast attacks do not work through staircases, because they are AoE attacks. Period. I would personally be cool with a house rule allowing them to go through and explode on the other side, but that's house rules, not official rules.

Steve-O said:

True enough (and Parathion's argument too).

Steve-O said:

AoE attacks are not actually defined anywhere though are they?
A Blast attack may actually not affect more than one space. That may depend on the results of surge spending. The surge spending isn't known at the time the attack is made through the stairs…

Blast still has a single target space. From that Target space it may (not necessarily) affect other spaces, but until it reaches that space and resolves it is only affecting that space, so it is only a single space attack.
This is different from Breath, Bolt, Sweep, Word and Word of Val, which all intrinsically attack multiple spaces and don't have a target space, but similar to Spirit Spear, which has a single target space but can always effect multiple spaces.

Note also that the FAQ says it is the radius of a Blast attack (ie not the attack itself, just the blast radius) and other AoE attacks that doesn't go through. (and elswere, Breath attacks explicitly cannot.)

Pg12
Q: Does the radius of a Blast attack or other area attacks (such as the Word of Vaal, Sweep, etc.) extend through a staircase?
A: No.
Pg3
…Breath attacks cannot be made through staircases.
Pg11
Q: Do the effects of abilities such as Aura, Spiritwalker, Command, and Kirga's hero ability (from Altar of Despair) extend through staircases?
A: Only non-area of effect attacks may go through staircases.

I think the last answer is just unfortunately sloppy (and we all should of caught it, but didn't.)

Not only does it fail due to AoE attacks not actually being a defined thing, except by casual usage (which itself has never been closely examined in difficult circumstances), but it fails in that at the moment of passing through the stair, some attacks are explicitly single-space target attacks that may later affect additional spaces.

To me, the wording is not at all clear.
To me the intended effect is that you can lob a grenade (in a limited fashion) through a stair (note that Dwarven Firebombs are single space attacks), but if the grenade goes off, the blast does not come back through (and nor does a flume of flamethrower go through in the first place). But the staircase does not retroactively prevent the grenade going through if it later explodes .

I don't generally like 'intent' rulings, but the wording here is sloppy and undefined in this respect, and so my preference is for the option that 'makes sense' over the option that does not.