What's your opinion. If it's a mod, include a link or map, doesn't matter.

"Difficultist."

I'd probably say that http://www.uesp.net/wiki/Skyrim:Siege_on_the_Dragon_Cult is a pretty challenging quest.

Orhttp://www.uesp.net/wiki/Skyrim:Discerning_the_Transmundane. Trekking through several Dwemer ruins and then Blackreach for hours is certainly lengthy.

The most difficult ( no such word as difficultest ) quest in my opinion is returning the thieves guild to it's former glory. It's both complicated and long.

I gotta go with the main quest. Not only is it relatively long (you can collect shouts for a long time, you gotta walk up to the Graybeards at least once) but also because of the fight with Alduin at the Throat of the World. Unless you are OP, that's a tough fight. You gotta keep him on the ground or he regenerates completely. He also calls the meteor shower (can't remember the proper name of the shout) and he does tons of damage. You have to win to keep the MQ going so there's no avoiding it. I've also run into a couple bugs during that fight that forced a reboot, and consequently, a lot of repetitious walking, seeing the visions etc.

Also, you can't quit and resupply past a certain point so the logistics can be challenging (both in terms of supplies and in terms of carry weight).

But the MQ is not exactly difficult is it, the player has their hand held for the entirety of the complete quest. Long yes, difficult no.

Meh, the game shields players pretty extensively in general, but that fight with Alduin at the Throat of the World is tough and unavoidable (unless you just skip the MQ).

One caveat - I haven't finished the Dawnguard DLC and fought Lord H. In general, though, that quest line feels shorter. You also have more help (Serana).

Agreed, the fight with Alduin on your 1st play through is fairly tough but subsequently becomes a walk in the park really. Lord H is a walkover really and the battle really doesn't live up to the build up the story gives it imo. I still go with restoring the thieves guild as the biggest pain in the neck the game has to offer, that and maybe curing Serana as a close second.

Agreed about the TG! That's a long, long haul (especially if you don't FT). I use the carriages so it's not so bad, but after the first time I did that quest, I kept notes on how many quests I'd done in each city. I initially thought the game keeps track automatically but no. I went back and forth sooooooo many times. Also, come to think of it, the fight with Mercer is pretty tough as well (especially if you don't have an AOE attack).

All good ones. Add The Legend of Red Eagle on that list.

I don't know if anyone would call it really difficult, but in terms of sheer length -- if we're talking about a single quest, not a quest chain -- Touching the Sky from Dawnguard seemed pretty damn long. Takes you through Darkfall Cave (and takes a while to reach that, if you haven't discovered any locations close to it), Darkfall Passage, almost the entirety of the Forgotten Vale, and then the Inner Sanctum, all the while carving through hordes of Falmer.

Even with Serana's help, that quest always takes me a while to push through.

I think someone already mentioned Discerning the Transmundane, but that's a long one. If you take the long way through Aftland to access Blackreach, it's pretty long. You can also spend loads of time in Blackreach before figuring out where everything is. Finally, you end up searching for those blood samples...

The dialog with HM is pretty lengthy too.

Yes, it's definitely "epic" in relation to the majority of quests in the game.

I always found HM to talk like tht and thought it was a bug, but nope. But always wonder why he talks so slow.

Agree, of course it depends at what level you do it, but it's still challenging, especially because at high levels the big boss (we're not in spoilers so I'll avoid the name) is accompanied by several powerful Draugr. In my current playthrough I actually didn't find him to be as dangerous as his fellow Draugr.

Longest - I don't know but I agree about Touching the Sky being very long though it's interesting. And many quests that require you to carry some item to someone, can get pretty long, if you don't FT.

I wouldn't argue difficult or even the longest quest, but I found Lost to the Ages (a Dawnguard side quest) a wonderful big quest - long, enjoyable and satisfying in that you get to help the ghost of a fallen adventurer.

I'd say Unearthed. Because it can knock your pocket change down a bit.

What I am about to say is my own personal experience. For me, the longest was building and decorating my house in Hearthfire. Took me forever with the going out in the world to earn more cash.

Good point - now that I think about it, I spent quite a bit of time doing this after getting Hearthfire. It was surprisingly fun (even though I asked my House Carl to decorate the first place before I realized you can't stop him and he stuffs the house with everything under the sun). Adopting kids and getting married were additional 'quests' once the house is set up so that stretched things out even longer.

I'm planning on migrating to a PC so I can play with mods and it's pretty exciting to think about how much Hearthfire will change/improve.

Difficult, I would say Siege on the Dragon Cult. At any lvl it is pretty hard. It is also my favorite dungeon, because it is always a challenge.

Lost to the Ages, is pretty long and can be pretty hard also. I might have said the MQ, but I consider that a chain of quest's or quest line.

I wont use cheats, so have never found all the gems.

definitely Discerning the Transmindane. I hate the falmer caves and having to get the blood of each race of elf afterwards. I also think the entire CoW questline is hard, even though Ive done it like 4 times. Its also pretty long.

No stone unturned

Dawn gaurd getting Auriel's bow. long as hell, dark ass cave, somewhat hard boss. hard to get out, lots of ice dragons and ice giants which are sort of hard enemy's if you are at a low level. lots of moving around mountains and rivers. but thats my opinion.