Mikel asks: Who is Arthas' sister?
Answer: Her name is Calia Menethil, and she is/was roughly 10 years older than Arthas. During Deathwing's attempts to worm his way into Human society and take over, his human alias, Davan Prestor, was to marry Calia. The marriage never happened due to Deathwing having other things to deal with. Calia has not been heard from since. There's rumors and speculation about where she may pop up next or the possibility that she may be in WoW right now, but it's all rumors and speculation and little more.
UncleVinny asks: Is there any lore reason why turning in a Fel Armament to the Aldor would make the Scryers hate me more? Aren't the Scryers happy to see demons killed, too?
Answer: The Scryers and the Aldor are both competing for A'dal's favor. By giving the Aldor your Fel Armaments, you're fueling their side and helping them get a higher standing in Shattrath. This is mostly a matter of perception since A'dal is quite accepting of all benevolent individuals. The perception of Us vs. Them is likely fueled by past bad blood between the Draenei and the Blood Elves.
From a storytelling standpoint, this situation was resolved with the formation of the Shattered Sun Offensive. Lore-wise, the Aldor and the Scryers probably do not mind much. From a game mechanics standpoint, they can't remove the Aldor and Scryer factions without screwing up a lot of older quests and such, so the gang war of Shattrath still exists.
Tran said: Dude, Arthas is 10 mannable? Lame. Discuss with lorefication!
Answer: I don't personally like the idea of Arthas being able to be killed by 10 people. It's rather anti-climactic for the biggest bad. What I would do is have him only be able to be killed in the 25 man dungeon. In the 10 man, you fight him to a standstill until he casts you all aside, and you can loot a chest as a reward for holding off the most powerful mofo in Northrend.
If they don't do something like that, well... eh. It feels to me like a serious dilution of the Lich King, but what can you do?
Ceej asks: I know so little on the Tauren's background. By virtue of the quests and instances you tend to undertstand at least a little background on most of the other races. But I find Taurens are skimped on.
How did they come to be? What were the exact circumstances of their alliance with the Orcs?
Answer: The Tauren origin story is In WoW, and most of the Orc-Tauren alliance information is in Warcraft III.
The Mists of Dawn is a story you can find on a wall in Thunder Bluff, in the Archdruid's tent. It is told in the style of a creation myth so cannot necessarily be taken at face value, but it's an interesting bit of flavor for the race.
The Orc-Tauren alliance was born during Warcraft III. When Thrall travelled to Kalimdor due to Medivh's urgings, the Orcs met the Tauren, who were in a bit of a bind with the Centaur. The Centaur were basically slaughtering the Tauren by the dozen, and the Tauren weren't especially unified at the time. With Thrall's help, Cairne Bloodhoof gathered the scattered tribes and beat back the Centaur. The Tauren have remained loyal to the Orcs, thankful for Thrall's aid. I strongly recommend playing WC3 to see this story unfold.
Camaris asks: What kind of Alliance/Horde forces were left on Northrend, if any? How remote is Northrend? Is it unchartered territory to the inhabitants of Azeroth? Did the Scarlet Crusade ever find out they were being led by a demon (in Stratholm Scarlet)? Ie, was there a quest where that revelation was passed on to.. well, someone? So err.. what do the Titans actually look like? Those statue-like things like Maiden are just constructs, or what?
Answer: That's a lot of questions! I'll make sure to hit them all.
First, we don't really know what's left in Northrend right now, but I can tell you what might be there. Remnants of Muradin's expedition and Arthas' expedition may be scattered somewhere throughout Northrend. If you don't know of those expeditions, give Warcraft III a playthrough. There's a good chance the Scarlet Onslaught is the remnants of the Scarlet Crusade's failed assault on Icecrown. We may also run into some Blood Elves, Kael's lackies that chased Arthas to Northrend, and possibly some Scourge that shook loose from the Lich King like the Forsaken did. Other than that, it's a pretty large unknown currently.
The very inner reaches of Northrend are likely mostly unknown to most of the world. However, Brann Bronzebeard travelled to Northrend at one point to find out what happened to Muradin. You can read more about this in Lands of Mystery.
We do not know for sure if the Scarlet Crusade ever discovered Balnazzar, but I would say there's a good chance of it. Dialogue involving Scarlet Commander Marjhan in Light's Hope Chapel seems to suggest someone other than Dathrohan or one of his lackies sent her. It also seems like it may have been done in secret, but this is just my interpretation. Maybe the Scarlet Crusade as a whole doesn't know, but many of the higher-ups do. There is no quest clearly stating this, unfortunately.
Titans look very Human-esque with skin of bronze and platinum. The Wowwiki page has a picture of each of the known Titans, so that's a good place to look. The Maiden of Virtue and similar things are likely just constructs built by the Titans or related forces.
Furinur asks: What's up with Katrana Prestor, King Anduin Wrynn's "advisor"?
Answer: Katrana Prestor is... Onyxia! This is a questline from before the Burning Crusade, which was the questline to become attuned to Onyxia's Lair. You reveal her identity, Bolvar shows the world how completely awesome he is, and then he sends you off to kill her.
CvijaFaQ asks: Why is Teron Gorefiend in Black Temple? What's the deal with RoS?
Answer: Teron Gorefiend has a history of being a really evil guy. After you 'resurrect' him, he probably just goes to the first place he can start wreaking havoc. Signing up with Illidan and hanging out in the Black Temple is just a logical place for him. He may also be there not for Illidan, but himself. Gathering power within the Temple to turn on Illidan later. After all, Illidan has the Skull of Gul'dan, a powerful artifact. Gul'dan was originally Gorefiend's mentor.
The Reliquary of Souls doesn't seem to have a very concrete, canon explanation. The most we can do is guess. It's possible the Essence of Souls is the coagulation of the Draenei that died in the fall of the Temple of Karabor. It may also be something they had under containment in the Temple. Maybe it's something that Teron Gorefiend cooked up. We don't really know. It's very mysterious, and interesting to think about.
Torash wants to know the name of the three Old Gods from the Sundering trilogy.
Answer: I do not think that any of the Old Gods but C'Thun have names. You may mean the demigods? Malorne, Ursol and Ursoc, Agamaggan and Aviana were all present at the War of the Ancients and ultimately died.
Fauche asked: Who the heck is Anduin Wrynn's father/Varian's wife? We know she exists, proof being Anduin himself, but we've never heard anything about her. Do you know anything?
Answer: Unfortunately, no! I haven't seen any mention of her, but if anybody out there has, I'd be eager to hear it.
That's all for now, everyone! If I didn't get to your questions yet, don't worry! I will answer you as soon as I can.