Unlike previous Castlevania games, Symphony of the Night is very open-ended, and you aren't restricted to arbitrary levels, but items still need to be found in a certain order to proceed (Except for Richter, who can proceed in whatever order he wants, since he begins with all abilities initially). That's what this walkthrough is for. This will show you the quickest way to get through the game, but that's about it. You should still explore the castle if you want all the goodies it hides. The Map Section is useful if you're just looking for a particular item or something. I have incorporated maps to show the locations of the major relics and bosses you'll have to face, and the quickest paths to them. Start at the "S", and end at the "E".
Prologue - Bloodlines
The game starts out with you as Richter, about to face Dracula in a re-enactment of the final battle of Dracula X. You can hit a switch at the top of the staircase for some items, but they don't really seem to do anything. Dracula's first form should be familiar to veterans of the Castlevania series, and his second form is of a giant demon (Holy Water's item crash works nicely on this form). You can't really lose this battle, but the better you do, the higher Alucard's stats will be. For maximum stats, don't get hit, revived, or use many hearts.
Part 1 - Defeat Slogra and Gaibon
You'll start the game off with some extremely powerful equipment, but Death will take it away quickly. But that's OK. Continue along through the Alchemy Laboratory and find and defeat Slogra and Gaibon. The Leather Shield might be helpful in this battle, since you can use it to block Gaibon's fireballs. The Axe Subweapon is useful here too.
Part 2 - Get the Jewel of Open
After taking care of Slogra and Gaibon, continue out of the Alchemy Laboratory and into the Marble Gallery. Along the way, in the "Clock Room", you'll meet Maria. Remember the location of this room, as it will be important later. Continue along to the Outer Wall, and make your way to Doppelganger10, basically, a clone of Alucard. You should be able to handle it without too much difficulty. Now continue up the Outer Wall, and go left into the Long Library. Here you can find the Master Librarian, from whom you can buy items from. Buy what you want, but be sure to get the Jewel of Open, which allows you to open the glowing blue doors in the castle.
Part 3 - Get the Leap Stone
With the Jewel of Open in hand, leave the Long Library and head back to the Outer Wall. You'll probably want to grab the Soul of Wolf while you're here, if you haven't already. Continue going up, and then turn left to find a teleportation room. Take it, and you'll end up back at the Castle Entrance. Now continue through the Alchemy Laboratory again, until you're almost at the room where you fought Slogra and Gaibon, but this time, head right, and through the Blue Door. You'll meet with Maria again. Continue past her to the Royal Chapel. Get ready for lots of climbing as you ascend up the chapel and the bell tower. Eventually, you'll be heading right again, and you'll encounter the Hippogryph, which shouldn't pose too much of a problem. You'll meet with Maria again after the battle. Continue on your way into the Castle Keep. Go right through the long corridor, then up and back to the left to find the Leap Stone, which allows you to double jump.
Part 4 - Get the Form of Mist
After getting the Leap Stone, head back to the right, then drop down and enter the nearby teleporter. Teleport back to the Outer Wall. Now, make your way back to the "Clock Room" where you first met Maria. Wait until the upper-left path opens up, then take it (If you have the Clock subweapon, you can stop time to reach the upper-right path). Continue on to Olrox's Quarters, then head left to the Colosseum. Make your way up, to the left, down and back to the right to reach the arena, where you'll meet with Richter and have to fight Minotaurus and Werewolf. This battle can be tricky, but like most boss battles in the game, it's manageable. After defeating them, continue to the right to find the Form of Mist, which allows you to turn to Mist and pass through grates.
Part 5 - Get the Soul of Bat
Once you have the Form of Mist, you'll want to return to the Long Library. If you bought a Library Card, you can just use that to return quickly. If not, just head back to Olrox's Quarters and head to the nearby teleporter and return to the Outer Wall, and return that way. Instead of visiting the Master Librarian, double jump and make your way to the Save Point. Continue going and you'll run across the Lesser Demon. This is a pretty easy boss battle, but to those of you who like collecting EVERYTHING, the only way you can encounter the Mudman enemy is by waiting for the Lesser Demon to summon it, so if you want a full bestiary, you'll have to do that. After defeating the Lesser Demon, continue along and you'll make it to a grate you can pass with the Form of Mist. Do so and grab the Soul of Bat.
Part 6 - Get the Echo of Bat
With the Soul of Bat, since you can now fly anywhere you want, you can technically go back to the Castle Keep, defeat Richter, and end the game. But if you do that, you'll be missing out on most of the game, so let's keep going, shall we? The next important item we'll want is in Olrox's Quarters, so teleport your way back there. Go up the long passage and head to the left. It won't be long until you make it to the this area's namesake, Olrox. He's not too bad, but after defeating him, he'll transform into a large green creature, which you'll have to face. Defeat his second form and continue to the left to find the Echo of Bat.
Part 7 - Get the Gold Ring
Now let's enter the bowels of the castle. Make your way back to the Marble Gallery. At the Clock Room, if you fly straight up, you can find the Gravity Boots, which allow you to super-jump, which is pretty nice. Go to the right, and if you haven't already, go to the room just above the long corridor, past the blue door, and hit the switch there, which will open up a couple of nearby passages. Now go back to the left and down, which will take you to the Underground Caverns. Go down just a bit, then head to the right, and you'll make your way to an odd teleportation room. Take it, and you'll be in some sort of dream sequence. Afterward, you'll have to fight the Succubus. Defeat her and you'll get yourself the Gold Ring, which will be vital later on.
Part 8 - Get the Spike Breaker
As you might have noticed, there's a lot to explore at this point in the game, but not much you have to explore. But if you're just following this walkthrough without doing any exploring, you're really missing out on a lot! Anyway, the next thing you need is the Spike Breaker. Head down into the Underground Caverns, and head left until you reach a wooden bridge with a Skeleton Ape on it. Lure the Skeleton Ape to the right and get it to throw a barrel at you to break the wooden bridge. Now you can drop down and reach the Abandoned Mines. Along the way, you'll have to fight Cerberos, which is pretty simple at this point. Continue along into the Catacombs. Keep going down, and when you have the choice between heading to the left or right, go right. Past the room with the slimes is a pitch-black room full of spikes. This is what the Echo of Bat is useful for. Transform into a bat, and use its echoes to navigate past the spikes. The room will be lit after you make it through. Now continue on until you come across the Spike Breaker, which is armor that will break spikes when it touches them.
Part 9 - Get the Silver Ring
Now return to the Abandoned Mines. If you're wearing the Spike Breaker, you can walk right through the previously dark spike room and watch it in action. Make your way to the teleportation room, and teleport back to Olrox's Quarters. Go to the left and back to the Royal Chapel. You may have noticed a room filled with spikes before... now that you have the Spike Breaker, you can make it through. Equip the Spike Breaker and walk through to reach the room past it. You'll meet up with Maria again and get the Silver Ring.
Part 10 - Confront Richter
We're almost ready to return to find Richter...almost. First, we need to return to the Clock Room in the Marble Gallery. Equip the Gold Ring and Silver Ring, and the clock will chime 13 times, and you'll be able to drop down. You'll find Maria again, and she'll give you the Holy Glasses. Now you're ready for Richter, so make your way to a teleporter and return to the Castle Keep. Now you can make your way back to where Richter fought Dracula in the Prologue, and you'll find him. Richter, as a Belmont, attacks with Holy attacks, so if you have Holy Armor or something like that equipped, you'll be fine. You can defeat Richter right now if you want (just like you could any time after getting the Soul of Bat) but if you want to progress, equip the Holy Glasses. You'll see a green orb floating around. This orb contains Shaft (you're damn right), who's controlling Richter. Destroy the orb instead of Richter, and you can continue. Head to the left and to the teleporter to make it to the Inverted Castle.
Part 11 - Collect Dracula's 5 Parts
The Inverted Castle is basically the same as the regular castle, but the enemies/items/etc. will be different. Since you already have most of the Relics in the game, you can feel free to go wherever you want whenever you want now. And you can return to the regular castle via the teleport room that brought you here, or by using a Library Card. In any case, there are five things you HAVE to get before the final confrontation: the five Dracula Parts (just like in Castlevania II), which are guarded by five bosses throughout the castle. Go ahead and collect them in any order you want while you're exploring. The map shows you where they are, here is what they are:
A: Ring of Vlad (Guarded by Darkwing Bat)
Part 12 - Defeat Dracula
Any time after collecting Dracula's 5 Parts, you can fight him. To do so, head to the Clock Room in the Black Marble Gallery. You'll then be able to access the area above you. In the room where you found the Holy Glasses in the regular castle, you'll fight Shaft. Shaft is simple, and goes down quickly. Then comes the final battle with Dracula. If you want, you can use a Library Card here to give your map completion percentage an extra .1%. In any case, Dracula's not too bad if you've done a good job exploring and have decent equipment and are at a decent level. If not, I would suggest that you do so. Also, feel free to use any and all medicine/food in your inventory... this IS the last battle after all!