After you get the Silk Bag and the Morning Star, you should go to Bodley Mansion.
If You Have an Oak Stake
If you purchased an extra Oak Stake in the previous mansion, you can take a much shorter path in Bodley Mansion to reach the piece of Dracula. If you do not have an Oak Stake, skip to the next section.
Go to the right from the entrance until you are at what seems to be a dead end. Some of the blocks in the wall are actually fake, so jump up to go through the fake blocks. Go to the right and use Holy Water to get rid of the blocks that are between the spikes and the water. Then you can jump across to the right.
Where the water ends, jump up to the right, then go right to reach a new area. Then go to the right until you find some stairs. You can go down those stairs or just walk off the ledge to the right. From there, go down the second flight of stairs. After that, go to the right and kill three Skeletons, then go to the right to find the chamber that holds the piece of Dracula. Use your Oak Stake on the orb, then jump onto the bag to get Dracula's Nail. When you equip this, you can break Holy Water blocks with your whip.
If you want instructions on how to leave the mansion, skip to the Leave the Mansion section below.
If you Do Not Have an Oak Stake
If you have no oak stake, you will have to take a longer path through the mansion to get one.
Go to the right until you find stairs. Go up the stairs, and keep going up the next several flights of stairs until you reach the top. From there, jump up to the right. Ignore the stairs to the right, and jump onto the raised platform with the Skeleton on it. From there, jump down to the right, then jump up to the next raised platform. Go to the right, where there seems to be a dead end. The upper blocks are fake, so jump through them.
Follow the path downward until you reach what seems to be another dead end. Throw Holy Water at it and go through. From there, keep going to the right until you find some stairs. Go down the first flight of stairs, then jump off the left side of the platform. You should go through some fake blocks in the wall. Go to the left from there and you will find the Gypsy who is selling the Oak Stake. Purchase it, then fall down through the fake blocks that are to the left of the Gypsy. From there, go to the left and walk off the left edge of the ledge, then go to the right until you reach the chamber that holds the piece of Dracula. Use your Oak Stake on the orb, then jump onto the bag to get Dracula's Nail. When you equip this, you can break Holy Water blocks with your whip.
Leave the Mansion
To leave the mansion, just go to the left until you find the stairs. Go up all the stairs, then jump up to the left, and walk left to reach the next area. Go up these stairs and go to the left, killing the two Skeletons, then walk off the ledge to the left. Jump left through the fake blocks in the wall, then go to the left to leave the mansion.