Even thought Lords of Shadow is a reboot, please pay attention and read everything with strict intention -
Lords of Shadow has many references to the Castlevania series in which most have found - others have not and still claim that this isn't a true title in the franchise and wasn't since the get go. I will explain that big budget actors will not pick up a script unless there is particular scent in flavor and serious cash is involved - this is the reason as to why theses actors chose to be apart of this story. Keep in mind some of theses will have added in tidbits in which I forgot to mention from the original posting. So you have been warned for serious spoilers.
Good games -
So the story goes that three people founded the Brotherhood of Light, which then, due to their studies had pushed them on to a crusade of sorts that forced them to ascend their pure sides, thus leaving their darker sides behind. A bastard son is born and abandoned on the door step of a church of this order and is taken in and trained to be a Paladin of this order, who is presumed to be Cronqvist blood, but takes the surname Belmont for his love towards the Carpathian Mountains.
During his quest we stumble upon something very interesting in what made me open my eyes to something. If one has played Aria of Sorrow, we come to find out that Soma Cruz had stumbled upon his unique ability and that was known as "The Power of Dominance" and it is this power in which Dracula used to have order and rule over the demon castle and other types of minions in which he used for his army. The reason why I am stating this is due to a very minor fact and reference found in Lords of Shadow - in Dawn of Sorrow, after killing one of the main antagonist, you will see what appears to be a dark soul enter the body of Soma. If you had purposely got the bad ending in this game and allow Mina to get killed you will see the exact same power enter him, this is the dark power that is Dracula and his power of dominion.
Now in Lords of Shadow - if you pay strict attention to the three relics that Gabriel had acquired during his quest - starting off with the Dark Gauntlet, after fighting the Black Knight, you will see this exact same reference as what I stated above. We all know Zobek had been purposely stalking Gabriel since the beginning and we knew that he easily twisted in manipulated him to murder two people. And since he is "Death", and have a full understanding of how both fictional and fantasy based Necromancy works. After Gabriel has defeated the Black Knight you will see this exact same dark essence enter the Gauntlet and then force it upon Gabriel. Well, apparently he "puts" it on... I honestly don't see him walking up to it and just "slipping" it on, it was forced upon him. As you can hear him scream in agony, the metal is being melted on to his skin. As the 'red' in this dark essence is a form of 'heat'.
Now the Black Knight was created by Claudia's father to protect her due to the Lycan threat. This creature required "souls" in order to survive. Well, how this creature was reanimated was due to a form of Necromancy because the being was sentenced murder. So in theory Gabriel has the hand of a murder, and in order to reanimate this being you will need to place a spell on it and then a necromantic seal on the armor. Well, in order for this 'ability' to had happened, this dark power was in fact the power of Zobek/Death himself using the "Power of Dominance" on something that has "Necromantic seal", thus Zobek/Death had "given" the Gauntlet to him. By doing so, Gabriel had be given the power of Death at the start of the game. So that's one Lord down.
"But oh no, jestercolony! They meant the God Mask was their pow---" No, the God Mask wasn't meant for power. As it only had given its wearer the ability to see through God's eyes (i.e his love, compassion, strength and wisdom; keep in mind I am not religious.)
Once you have paid attention to the Dark Gauntlet scene and that dark essence - which is seen in Dawn of Sorrow, has now been infused to him, his skin melting. This same concept applies to the Cyclone Boots of Cornell and the Seraph Shoulders from Carmilla. Because take notice before he reclaims three pieces, he had already 'claimed' their power. The two Mask had been simply used as a tool to manipulate Gabriel from the very beginning. As for the gauntlet, well... If you take in to key factors already and can easily see it then, congratulations! If not, take notice to some of the fights where he actually uses this gauntlet where he touches the lords (i.e He punches Carmilla in the face!)
Now we need to talk about the three founders. They had been sent out on a crusude in order to ascend. But yet left behind their darker halfs. The reason to this is that they are now considered necessary evils, due to the fact of the Bernhard summoning The Forgotten One, who is considered a true evil due to the fact that he is a sovereign of the elemental Plane of Darkness. In order to combat this being, Holy powers just won't cut it anymore, you need evil that can fight evil. Upon sealing away this creature they had been given the Mask, which was broken into three pieces - due to the fact a truce had been made not fight over their share of the halfs. This is known as a fragile alliance (as you can see why Orlox is feeding on the blood of Lycans.)
Cornell, with the aid of Zobek had taken Agharta, this was known as the Necromantic Wars, in which (I assume) they had stopped caring about the evil creature all together.Carmilla took control of the Demon Castle, due to having some humanity left in her (keep in mind she is a vampire after all.) and stayed to be the Castle's keeper and jailer of this creature and the Demon Castle and is also due the reason as to why she turned Laura is due to the fact she was never able to have child in human life.
The next aspect of what we are going to talk about is another very important plot detail that really had gone unnoticed. The story isn't just based on Gabriel's personal vengeance, the story is also about Rinaldo Gandolfi, who created the combat cross because his "Wife" was murdered by Carmilia and his daughter Laura had been taken from him and turned. He created the Combat Cross and hid the relics away just in case someone would follow in his footsteps for vengeance on theses evil beings. I assume that if Gandfolfi is still alive - it is either because of the fact he is either turned (hence why he is able to survive in the land of the dead) and or the fact he is around 100 years old and hence in the log it is stated that he is old and senile, but still has a lot of knowledge. - which makes me assume that Laura is at least a century year old and the only reason as to why she is able to keep her mortal appearance is because of her pure innocence.
Next we find out the son of a bastard is left on a monastery, who is taken in by the Brotherhood and trained to be a Paladin, assumed to be of Cronqvist blood, who in which is manipulated in to murdering his wife (Woman 1) by the Devil's Mask and is led to believe by his elders to go on this quest. He then murders Claudia (woman 2) and then is infused with the Dark Gauntlet (as stated above.) Prior before theses events, we have Pan speaking to him in riddles of warnings of Gabriel's ignorance and arrogance and continues to fail to see the truth.
Upon meeting Cornell, who attempts to try and tell Gabriel the truth and simply tells him to leave and back the hell off,who in return becomes ignorant and claims that he will reunite the "three powers", in which in his hand and order think that it is the God Mask. Cornell just laughs at him and they fight. If you watch carefully - Cornell bites him (Bite 1) during the battle. Then of course he is then bitten by Brauner (pay attention his grab QTE; bite 2) and is then confronted by Laura, see's the weapon and the spirit of he and his wife talking before her out of love. Seeing the weapon she quickly remembers her mother and "Father" understands as to why Gabriel is now here. He is then confronted and then bitten by Orlox (bite 3.)
And then confronts the Dark Lady, who is being stalked by Death himself. She some how knows who Gabriel is either due to Laura (vampires do share a psychic link to each other in lore.) or she is a tattle-tale; the castle itself spoke to her (it is a creature after all.) or it is either Satan, Death or her other half. Keep in mind that Cornell had to have aid of his Lycan troops to warn him of his coming. She then attempts to lure Gabriel to her cause, because she KNOWS exactly what is going to happen. "There is no resurrection, only this living death you see before you." is what will pretty much give it away, due to the prophecy. She an all out attempt for him to be her King, her...champion instead he turns away and kills her. Not forgotten the fact, that she too bites him.
The King of Angels then speaks to Baba, in which tells Gabriel of his coming, she is aided by him of course, but is quickly killed off by Zobek/Death because of the fact she may reveal who in which he really is. And of course - Gabriel commits an act of deicide by killing Pan at the very end. It is here we find out that Death manifest from Zobek, in which tells Gabriel the truth that he in fact did unite the three powers and allowed him to obtain the God Mask. Now keep in mind that Zobek wants power - and you have to remember what The Forgotten One holds. Welp, turns out Satan said "Screw you buddy. I just used you to get the mask." and pretty much burns Death away.
Gabriel is then granted life and angelic powers to combat Satan. Who is quickly put away, but finds out that his very own wife lies to him and takes the God Mask, but the Devil's Mask remains in which Gabriel still holds. After the battle Laura calls out to him out of feat due to the seal of the true evil has weakened due to the other two lords being dead (the reason why I do not count Zobek because he is neither mortal or undead, he is DEATH; very complete difference.) and the two grow close because of her "fathers" quest. This is when Gabriel finds out the truth that He, the three founders had all been used and lied to by God and Satan. Gabriel has it worse due to his wife. It is here that he begins to hate God. He is then told that he must become a being of pure evil in order to enter the dimensional prison. Laura then bites him (Bite 5) and then tells him to drink her blood or he will die. Doing so, he then kills her instantly, in theory he has now drank the blood of the innocent (Woman 3.)
He then proceeds to enter the rift. Here this is another Aria of Sorrow reference in which this is could be the Chaos Realm within the castle, a place where only Dracula can enter. It is here he battles The Forgotten one with nothing but pure hate and rage in his heart.
So lets look at the facts -
1. The Dark Gauntlet has a Necromantic Seal on it, which allowed Death to use the "Power of Dominance" on Gabriel and control him, in the end. Also mentioning the use the Mask to manipulate him into murder. As stated in order for a Necromancer to have control, it must be bounded to necromantic magic (or a seal.) And since he is has the "hand of a murder" and has a seal, Zobek gave the power of Dominance. How did he control Gabriel in the end? Its because the Gauntlet was bound to Gabriel which in return was bound to Death, which since Gabriel didn't have the power of Necromancy known to him he had no chance in fighting back, the only thing he could do was die.
^- Necromancy occutlism fiction and fantasy 101
2. He is bitten by the first Lycan and Vampire, 3 highborn, 2 of which are "demonic" vampires and then murders three women. This why I made the bite reference - next you will want to take notice of the three women he murdered. Dracula had three wives - do I need to really say anymore? Now keep in mention this really has nothing to do with being married. I simply state the 3 wives thing as a fun fact.
3 The Blood of the Innocence factor.... In Castlevania lore Dracula needs the blood of a virgin in order to be resurrected pre-maturely or needs it to regain his full strength upon his 100 regeneration cycle.
4. During the final battle with The Forgotten One, being consumed by nothing put pure hate and rage, Gabriel makes his final attempt to leap over the creature - if you pay attention WHAT hand does he use to touch and absorb his power? You guessed it - the Dark Gauntlet. After absorbing the power the creature kneels before him and calls him his "liege", and begs for mercy. Gabriel kills him instantly and then crushes the Combat Cross with the very same hand and leaves it in the "Chaos" realm. In the original canon (again another Aria reference) the whip was sealed inside to keep Dracula weak. Well, Gandolfi still has a VERY important roll to play in the story later, now doesn't he? It isn't the OFFICIAL Vampire Killer yet. Hence why the Dark Gauntlet was granted on to him the Power of Dominance in which was bestowed upon him by DEATH.
5. Dracula is said to take the form of Bat, Wolf and Mist... Hmm, 5 bites... three forms... Bat = Vampire, Wolf = Cornell and Mist = Death (poison cloud; this is also considered another vampire power.)
My true speculation? We don't know what's going to happen yet due to the fact the Demon Castle is far bigger than what we have been shown - 2ndly it is a Creature of Chaos, it is a chaos entity and is why it is able to change forms (<-- paranormal/demonology studies 101.) He isn't Draucla yet - and honestly I think its time he cleans his house up. The castle itself still has many other demons in which he needs to conquer and perhaps the famous Chaos demon itself before he proclaims himself "LORD" of his Castle. So I'm not going to be surprised in the next game that it will more than likely will receive a huge bashing from religion sects and people due to the fact we will more than likely be killing christian knights/paladins and clergyman due to the fact he (Gabriel) hates them now as we as slaying the other threatening demons in which the Bernhard Family has summoned so that he may have dominion over them.
And yeah... He does fuse with the Devil's Mask - Slogra and Medusa's are seen in the ending as well as Gaibon but their shapes have changed. Slorga has remained the same - they are not animated because Zobek isn't a threat to the "Prince of Darkness." So if you still don't understand what is going on, I highly suggest you read all the lore in this game and take a look at past Castlevania references.
I hope this helps you understanding the story of Lords of Shadow.

good games!