Plot summary: You are Soma Cruz. Last year you found out you are Dracula and that you can absorb souls to use for your own purposes. You've overcome your inner chaos and are now a productive member of society again. Well, you're still a student but let's assume that's somehow productive. One day you get approached from a priestress of the "Enlightened" who says the grace of God won't work without the presence of a devil and that since you're not doing your job as an evil overlord she'll make you turn evil or kill you and get a replacement. You fend her off but want to know what exactly they're up to so you sneak into their hideout, which just happens to be a replica of Dracula's castle. Feeling at home already?
Gameplay: Mostly platformer with fighting baddies, the path you take isn't completely linear and as you're busy kicking ass and taking souls you gain new abilities. That's the interesting part: Any enemy (save for human bosses) can lose his soul upon death (random chance) and if he does so you'll get the soul, which usually gives you a new ability. Bosses will always drop their soul since you can't fight them again. Most souls need to be equipped to be of any use, you have three equipment slots for them. Projectile, which is an attack (shoot something, summon something, throw something, etc) in 95% of all cases. Guardian, which can be many things from transforming into a bat to summoning support monsters (some continuous attacks, e.g. a beam, fall under this, too) but always uses mana while in use. And Support, which is usually some kind of stat boost or immunity to some condition. Some souls grant you new moves (e.g. double jump, walk under water) and don't need to be equipped. One soul allows you to have two sets of equipment (both souls and physical junk) you can switch between so you can have one combat set and one set that just contains abilities needed to progress past certain points (e.g. you'll never want to change into a bat in mid combat but you'll need the transformation to get through some holes or reach some platform). Some souls become stronger when you collect them multiple times.
The castle can be explored freely and your progress is usually blocked by some kind of obstacle that can only be overcome by taking some boss's soul. Kinda like Metroid but with fewer obstacles (sometimes only one or two for one ability) and no sequence breaking. Some obstacles need souls from normal enemies to get past but there's only one case where such an obstacle must be passed to finish the game, most just block off some bonuses.
You can also equip various weapons, armor and accessories. The weapons now include guns and throwing weapons. The game seems to be designed for the use of a melee weapon, though, since I had little trouble slaughtering even bosses by using throwing weapons together with the boomerang skeleton (increases ROF and damage for throwing weapons) soul. The handguns are pretty useless because they deal less damage, are expensive, have less range, a lower rate of fire and don't strike through enemies unless you use the special attack which eats lots of mana compared to throwing weapons. Ah, yes, every weapon has a special attack. Most are worthless, often you take a step forward and attack instead of just attacking and you spend a lot of mana on them. The throwing weapon special is the worst, you'll throw a fast shot but it doesn't do more damage and it takes longer until you can shoot again. Overall just avoid the A button.
Some weapons can be turned into more powerful ones by using souls. You'll have to do that if you want the better stuff because you won't find any of the powerful weapons in the castle or store. Since ranged weapons can't be upgraded I only used that upgrading deal once and never really took advantage of the new weapon. The store gets the last load of new items roughly one third into the game so if you're like me and use ranged weaponry you'll use the throwing sickles for the largest part of the game.
It's a bit annoying that the most used button, B (jump) is "cancel" in the menu and A (special attack) is confirm, I found myself cancelling when I wanted to confirm just after opening the menu and executing special attacks instead of jumping after closing it, especially since in the previous game, the jump and confirm button were the same one. That went away after a few hours.
The touchscreen is used in order to break certain blocks, draw magic seals and give orders to summoned creatures. The magic seals might need explaination: You need to pick them up to enter a boss room, then, when you've beaten the boss you must paint the seal on the touchscreen or the boss will regenerate a bit. The seals are just a few dots in a circle you need to touch in a certain order (but you have to do it in one stroke) and can easily be done with your index finger (no need to drag out the stylus). You might want to practice them a bit though since you'll mess them up more easily when under pressure. Overall I've got them right more often than not and the system seems rather forgiving, as long as you touch the dots it doesn't matter what shape your lines have. For example, one of them starts with a hexagon but you can just as easily draw a circle. The top screen shows a map or your status and the data for the last enemy you attacked. It's a bit annoying that you can't see the name of an enemy while in map mode but it's minor.
The only let downs were the length (I had 8 hours of playtime recorded on my savegame when I beat the final boss) and the last boss, who has lots of hit points but has very simple attacks that are easy to avoid. I was chopping away at him for minutes until he went down.
Compared to Aria of Sorrow there's more emphasis on ranged weaponry, less items to be found in the castle, some souls are harder to get (lower chance of drop), less bonus for levelups, the souls scale better with your level and the more powerful ones cost less mana, poison got nerfed, your mana regenerates much faster and a much improved Julius Mode (though it's less useful for speedruns than AoS's because it includes proper levelling instead of just becoming stronger when you beat a boss) (an unlockable play mode). Oh, and you can finally buy items in quantity instead of pressing buy once for each potion you want.
Graphics: The DS easily proves itself superior to the GBA. Huge, detailled enemies, complicated special effects and even some polygonal backgrounds make DoS look great. Slime now conforms to the surface it's on, enemies often break into parts upon death and there are lots of particles flying about. I think the many summon enemy spells only became possible because the DS can handle a much larger number of baddies.
Sound: Good. The music is pretty good and some themes just plain rock. The screams as you slaughter the enemies sound much clearer than on the GBA, as do the few bits of voice that happen every now and then.
Advice: A definite buy for anyone who likes jump and runs with weapons and probably even those who don't. Oh, and if you have Aria of Sorrow, make sure to plug it into the GBA slot when you start the game, you'll get the Rare Ring (increases chance for ph4t l00t).