Read Prima's complete Castlevania: Lords of Shadow 2 walkthrough.
Head across the steel girders onto the next platform, drop down to the area below and head toward the gate to initiate a cut-scene. Go up the stairs and into the next room for another cut-scene, followed by a battle against two Bloody Skeletons. One holds a shield that must be destroyed with the Chaos Claws. Once that task is complete, switch to the Shadow Whip and attack the enemies at maximum range. Dracula cannot drain their blood, so you never need to close in on the enemies. When it seems as though they are defeated, they turn into a puddle of blood. Use the Sustained Whip to hit the puddles of blood and finish them off.
After another cut-scene, Dracula is placed in an area divided into four rooms with four glowing yellow crosses on the ground. Carmilla patrols the rooms looking for Dracula. You must offer Dracula's blood at all four crosses to open the door and proceed with the story, but there are two traps involved. If Carmilla spots Dracula, she summons two enemies to attack that must be defeated before you can continue.
If Carmilla reaches any of the crosses Dracula has already offered blood to, Carmilla will offer her own blood and reset the cross, meaning Dracula must offer his blood to it again. In addition, Carmilla will remove the bookshelves that allow Dracula to hide from her, and she'll grow tired of the search and teleport from one room to the next in an attempt to quickly spot Dracula.
The best course of action here is to get to the closest cross and offer blood as quickly as possible. If Carmilla enters the room, hide behind a book shelf until you can make it into an adjacent room. If she is about to reach a cross that you've already covered, allow her to spot Dracula. While you'll need to fight the enemies that spawn, it will prevent Carmilla from resetting the cross.
Once all four crosses have Dracula's blood, head through the newly opened door, and offer Dracula's blood at the cross on the ground. Continue through the next door and access the statue to replenish Dracula's health if need be. Head to the right and climb the right wall at the end of the hallway. Make your way around the outside of the castle, then back inside to find another Pile of Sacrifice, which yields a Kleidos.
Drop back down and head left through the open doorway. Immediately to the right is another fallen knight. Interact with him to obtain a Soldier's Diary entry, then head down the path to be faced with a choice between two Maries. Drink the blood of the Marie on the right, then prepare for a boss battle against Carmilla after a short cut-scene.
Boss Battle: How to Beat Carmilla
The battle begins with Carmilla in a hamster-like ball made up of several circular strips of metal. Switch to the Chaos Claws and attack her relentlessly. When she begins speaking she is preparing one of two attacks. The first is a grounded lightning shockwave that extends from the ball in a small radius around Carmilla. This is fairly easy to jump over to avoid taking damage. The second attack is unblockable and thus features the telltale red circles. When you see this visual indicator, Carmilla is about to lunge toward Dracula with a linear attack. Back away and dodge this attack, then dodge toward Carmilla to close in quickly and continue your attack.
With continuous attacks, the sphere bursts quickly the first time. However, Carmilla quickly creates the sphere again and summons two enemies to assist her. Ignore the enemies unless you need them to replenish your Chaos Magic. Focus exclusively on Carmilla, attacking her nonstop unless you need to evade an attack. It's important that the sphere remains a shade of orange to indicate that you're making progress. If it changes back to blue, you aren't attacking frequently enough.
When you destroy the sphere completely, Carmilla attacks normally with her lightning. She uses it as a linear attack that extends along the ground. This can be dodged or you can jump over it. She also uses the circular lightning attack that hits in a small radius around her, just like before.
During this phase, you cannot attack Carmilla normally. Instead, you must use a Void Projection to freeze her in place, then attack with your strongest available Shadow Whip skill. Do not use the Chaos Claws because they melt the ice too fast and won't inflict as much damage. Once again, ignore the additional enemies unless they are getting in your way and you're having difficulty focusing on Carmilla.
After three or four freezes, Carmilla should shift into the next phase of the battle. In this phase she splits into several clones of herself. She attacks with two back to back circles of lightning that move slowly across the ground as the circles get smaller. Jump quickly to dodge these, and attack the Carmilla clones. The clones go down with a single swipe from the Shadow Whip.
Once the clones are dead, attack the final Carmilla to see another quick cut-scene in which Dracula gains the power to transform into mist. Follow the on-screen directions to escape Carmilla's grasp, then use the Mist Power to enter Marie's cage and drink her blood. Use the Mist Power to exit the cage and engage Carmilla.
During this final phase, use the Shadow Whip from maximum range. When the demon appears over Carmilla's head, quickly dodge back. The demon has two attacks, the first consists of two quick swiping attacks that cover a wide radius in front of Carmilla. A quickly dodge back evades this attack. The second attack consists of two linear lightning attacks that travel along the ground. It's similar to Carmilla's previous linear lightning attack, but much faster, meaning you need to dodge twice in rapid succession to avoid it.
When the demon is not present, attack relentlessly with the Shadow Whip until Carmilla is defeated. You now have the ability to turn into mist, which allows Dracula access to many secrets that have been locked behind bars until now.