Estimated achievement difficulty: 7/10
Offline: 38 
Online: 0 
Approximate time: 90 Hours (less if you already did DS2)
Minimum number of playthroughs needed: 3 (or 1 1/2 and Covenant boosting)
Missable achievements: Yes - Lucatiel (though can be done on NG+)
Does difficulty affect Achievements: No
Unobtainable/glitched Achievements: No
Extra equipment needed?: No
Welcome to another potential bevy of deaths in Darks Souls II. This game doesn't seem quite as challenging as the first, but that may be because most players now know what to expect, you will still need a decent level of skill and perseverance in order to get the full 1000. If you have already completed Dark Souls 2 then be aware that Scholar of the First Sin has changed enemy, NPC and item placements so it can mean things are not exactly the same. Plus, you need to get all of the new DLC spells to get the relevant achievements as well. Still, if you already completed DS2 then this game should hold few surprises and you could possibly complete it in 30-40 hours if you rushed through it.
NOTE ABOUT ONLINE: I've put this game down as fully offline, which is true to a point. In order to get the achievements for all spells you HAVE to get Rank 3 in the Heirs of the Sun Covenant and the easiest way to do that is to play online and use the White Soapstone to be summoned to help other players defeat bosses and get Sunlight Medals in return. HOWEVER, you can get these items as very rare drops from a number of enemies so it is possible (but amazingly time consuming) to do this offline if you so wish.
- Random drop from the Dark Giants (ridden by hollows) in Harvest Valley.
- Random Drop From Falconers in starting area (NG+), near Ruined Fork bonfire in Shaded Woods and in Brightstone Cove campsite (all playthroughs).
- Can be obtained by helping another player beat a boss while in the Heirs of the Sun Covenant
- Can be obtained by defeating a boss with a player who is in the Heirs of the Sun Covenant (can get more than one if you summon multiple Sun Bros)
- Can be obtained by phantom after summoning time limit expires (Phantom Duty Fulfilled) while in the Heirs of the Sun Covenant
Likewise if you are prepared to grind out 500 invasion kills for EACH of the Blue Sentinels and Brotherhood of Blood covenants (for the spells Rank 3 of each gives you) then you can get away with only one playthrough of the game, plus a partial one for the boss souls needed for NG+ spells. It is actually less time consuming just to play through the game a couple of times. Again, your choice. The only other Covenants required (Pilgrims of the Dark and Bellkeepers) can be done offline at your leisure.
The only missable task is for Lucatiel as you have to speak to her at set points and ensure she survives certain fights in order to get her gear as she vanishes after you last chat in Aldia's Keep (which isn't the case with Benhart). Though you can do this task in NG+ or later but it just makes your life harder than it needs to be. Likewise you could TECHNICALLY miss out on getting the items from other NPC's, or the achievement for getting them all in Majula, if you go around killing them. SO DON'T KILL ANYONE.
Walkthrough is here. This playthrough should see you trying to find EVERY covenant, kill every boss, find all NPC's, find all gestures and get ALL spells barring the ones that are NG+ or NG++ only.
Be sure to join and complete the following Covenants for spells (Heirs of the Sun - Rank 3, Pilgrims of the Dark - Rank 3, Bellkeepers - Rank 2). Go here to find out good methods to do so.
Be sure to keep ALL boss souls rather than using them and trade them to Straid (in the Lost Bastille) for unique spells. Note that you do NOT have to be able to use the spells - merely have them in your possession. A list of all spells can be found here.
ALWAYS speak to all NPC characters until they repeat themselves, as many of them will give you items, teach you gestures or move locations (to further their story) when you do so. This is needed to learn all gestures and get everyone possible to Majula. See here for help on both.
King Vendrick is an optional boss at the end of the Undead Crypt so read his specific achievement guide for help on defeating him.
It is advisable to do the DLC portions, for the spells you need, on the first playthrough as they are increasingly difficult on NG+. In order to access them you need to go to certain areas and have the correct key.
Crown of the Sunken King - warp room located behind Primal Bonfire in Black Gulch. Item needed to open door is found behind the door in the well in Majula (easy access via Gilligans third ladder) but you need the Forgotten Key to open - key is obtained by killing the two giants down the hidden drops in Black Gulch.
Crown of the Old Iron King - located behind Primal Bonfire in Iron Keep. Need Heavy Iron Key which is found on the same corpse as the Rebel Shield in Forest of Fallen Giants, in the central fire pit with the Salamanders. Can either use Cat Ring to drop in from above, or Iron Key (found in first room of Iron Keep on corpse under flaming statue) to open door near to where Last Giant was.
Crown of the Ivory King - access via Shrine of Winter (need four primal boss souls to open), key is on a corpse near to Drangleic castles first bonfire.
Once you defeat the last bosses (at the Throne of Want) you will be asked whether you want to start a NG+. Select NO and head back to Majula to finish up any tasks you need to (you can speak to Cale in the mansion for an achievement now you have beaten the last boss) and buy any items/spells you would like. All merchants replenish their stock on NG+ so buy up rare things you may need. Once you are ready for NG+ then the option to start it will appear when you rest at the Majula bonfire.
2nd + 3rd Playthrough
All of your stats and items will carry over to a new game (barring any keys or key items you have). On the second playthrough each of the main bosses guarding a Primal bonfire will give you a different unique soul (you can also get these souls by using a Bonfire Ascetic in NG, but as you need to do another un don't bother). DO NOT USE THESE. Trade them to Straid for more unique spells that you will need. Though you can skip some of the optional bosses this time around if you would like to. You will still need to play through most of the story though, and defeat the final boss, in order to get to NG++ (unless you feel like maxing out the Blue Sentinels and Brotherhood of Blood Covenants on either of the first two playthroughs).
On NG++ you need to get to Drangleic Castle as quick as possible, so either light the Primal bonfires and head through the Shrine of Winter or use the shortcut method that requires you to delete the update. Either way you need to speak to Chancellor Wellagar who will now stock the spells that could only previously be acquired by slogging through the invasion requirements of the Blue Sentinels and Brotherhood of Blood. Once you buy these you should have every spell and then snag the Dark Soul achievement.
Congrats on doing it all again.
[XBA would like to thank jackanape for this Roadmap]