A European prince terrorizes the local peasantry while using his castle as a refuge against the "Red Death" plague that stalks the land. The Masque of the Red Death
Vincent's limit breaks are a result of Hojo and Lucrecia's experimintation. They strike me as being oddly similar to Jenova and mako which can cause a person to change into monsters. However, there is little said about what actually happens with the experiments on Hojo's side. He meant to torture Vincent, which I think he did. Lucrecia meant to save him, which she probably did but in a no less twisted way than Hojo. As far as actual mako and Jenova being involved we do know that it was Hojo's trademark and pet project. But, Vincent lacks any of the definitive traits of SOLDIER (which is at the heart of the Jenova project). So while it is likely that they are similar, I doubt they're the same. After all, Cloud's big thing is the mako glow of his eyes even though he underwent an experiment different than SOLDIER. I assume, at the very least, Hojo was a capable scientist continually trying different methods to perfect his theories.
Ideally, I'd like to think that every person has a little bit of a monster within them that helps them get through the worst of times. Although, it might be a stretch to think of Vincent's limit breaks as genuinely benevolent since using them is risky. However, I think it fitting that the otherwise quiet and stern Vincent is able to transform into more. His apparent inaction is what caused his sins and this could be why Vincent cannot control his own limit breaks (at least until much later). When using his limit break he gets a boost in health, strength, and defense but becomes uncontrollable. On a side note, Vincent's limit breaks are horror based and I admit this is one reason I love him.
Galian Beast
The Galian Beast represents the horrors of nature, from voracious monsters and beasts in the world outside of civilization. Final Fantasy Wikia
Vincent's first (defualt) limit break, it also makes an appearence in Dirge of Cerberus. It reminds me of a small behemoth (in color scheme, originally) and later as a more wolf or doglike creature. It is fired based, which I associate with rage or passion, perhaps hinting as his original desire to save Lucrecia or get revenge on Hojo. On the other hand, it could represent the beasts within nature and how we all might be a little bad. In Dirge of Cerberus, Vincent is able to transform into and out of Galian beast at will, showing that he has mastered the beast within him. He is one of two returning limit breaks when Vincent takes center stage.
When Vincent awakens on the table in dirge of Cerberus he sees his claws. He knows he is no longer human. Although, it is unclear as to how Vincent really ended up in the coffin, I would assume shock is a good reason for him to black out. Perhaps he was sedated again and later stuffed into the basement. I doubt Hojo would have put himself in danger, so I think that as Vincent came to he was. This gave Hojo the chance to sedate him again. This is the only way my mind can grasp how or why Vincent would be locked in the basement. But maybe Vincent thought it better to hide away knowing he couldn't control the beasts within.
Death Gigas
The Death Gigas represents the horrors of science, creatures born of the unknown and accidents of experimentation. Final Fantasy Wikia
Death Gigas is a lightning based persona, one that has always reminded me of Frankenstein. With the exception of being pieced together from the corpses of criminals there is a particular passage that describes the creature in Mary Shelley's Frankenstein. How can I describe my emotions at this catastrophe, or how delineate the wretch whom with such infinite pains and care I had endeavoured to form? His limbs were in proportion, and I had selected his features as beautiful. Beautiful!--Great God! and his hair was of a lustrous black, and flowing; his teeth of a pearly whiteness; but these luxuriances only formed a more horrid contrast with his watery eyes, that seemed almost of the same colour as... are the two sections in particular that while reading Frankenstein I went, "This book is about Vincent!" It is rather fitting that is should represent the horrors of science and creatures born from the unknown because Hojo used Vincent as a labrat. In particulary, I find it particulary fantastic that it is lightning element because it is lightning that arguably gave Victor Frankenstein's creature life. It's become a bit of a joke between my sisters and I that I love Vincent because I love monsters and vice versa.
I am actually quite fond of Frankenstein's creature. He was a loner not because he wanted to be. He learned from people by watching them and longed to be accepted, but could not be because of his looks. He was refused companionship because of his birth. Victor even shunned him. The creature's desire for companionship eventually led him to seek revenge on his creator. It wouldn't be too far of a parallel to say that after everything, Vincent felt the same way. Hojo was the reason Lucrecia denied him. Hojo took what was most precious to him. Like the creature, Vincent felt the need to make the scientist pay. Vincent also tends to be a people watcher, gathering as much information as he can without saying anything. He also seems to know quite a bit more than people give him credit for.
Hellmasker
Hellmasker represents the horrors of society, serial killers and psychotic murders born from the cruelties and evils that mankind can spawn from their sins and vices. Final Fantasy Wikia
I have always had the least to say about Hellmasker. One, because I've never liked the Friday the 13th series, two because, I rarely used it, and finally, after playing Final Fnatasy 6 I always think of Edgar. Anyways, this limit also makes sense within Vincent, representing his ideology to get revenge on Hojo. Thus this persona might emerge from his sins and his desire to set things right, but since he can't control it, it becomes a poison or blotch, harming those around him. Other than Chaos, I consider this limit his most detrimental or malevolent.
Hellmaskers attacks are status based. For me this hints at the idea of things that take over and slowly kill us. Like poison or madness, steadily working its way through our cores until we are rotten or decayed. It shows, for me, the steady decay of mind and spirit.
Chaos
Chaos represents terrors of the occult and divine, devils, demons, the horrors of the spiritual underworld, and harbringers of the end of existence. Final Fantasy Wikia
Vincent's last limit break, it is dark based. He recieves this from Lucrecia's Cave in the original game. In Dirge of Cerberus, Chaos still slumbers within him as Omega Weapon's Harbinger of Destruction. He is the judge sent out to wipe out mankind so that Omega can destroy the planet. This creature was supposed to save Vincent's life after Hojo's experiments. Though it seems that after Vincent was shot (and dying) that Lucrecia could have experimented on Vincent first, giving him Chaos. Later Hojo could have added creatures to the list. But, I have always believed that Chaos came after Hojo's experiments rather than ultimately led to them. Either way, the idea for Chaos being horror for the occult makes me smile. Chaos in general is portrayed as a malevolent force within the Final fantasy worlds, it is only through Vincent that Chaos ever takes a side with the good guys. Although demonic looking, the spiritual can serve both sides without being detrimental. I think that through Vincent's struggle with Chaos he is made a stronger man and able to cope with his percieved sins much better. I also find it intriguing that Chaos is meant to be the destroyer or ender of civilization and humanity but it is only through Chaos that Vincent lives and survives.
There is some confusion as to which experiments came first: Hojo or Lucrecia's. As far as I am concerned, Hojo's came first, but Lucrecia didn't help the matter any. I think that the being that saved Vincent's life in the end was Chaos. Thus Lucrecia achieved her goal of saving him. Even though she was trying to save his life, for me this makes her only a little less twisted than Hojo. I feel that she was driven more by guilt (over the death of his father then his possible death) than by affection to save him. I assume she cared for him, yes, but not to the extent he cared for her or to the extent that she felt the need to atone for.
In addition, Chaos is not presented as a base ability. Instead he is presented as a manual that Vincent acquires after meeting with Lucrecia again. It becomes a sort of parting gift along with the Death Penalty. I don't believe that Vincent ever felt as though Lucrecia meant to do him harm (as well he wouldn't with as much bias he carried around for her). Based in the original game, I feel that Vincent welcomed Chaos. This is not true for Dirge of Cerberus in which he spends most of the game struggling for dominance. Chaos is defined as a different being all together in comparison to the other three limit breaks, of which only Galian Beast gets any screen time. Chaos becomes the controlled being and Vincent uses this form to defeat Omega Weapon.