Isaac

Isaac is the central villain of Castlevania: Curse of Darkness. A seemingly bondage- and self-mortification obsessed Devil Forger, Isaac lures Hector back to Castlevania in order to make him the new host body of Dracula. He does this by arranging for Hector's wife to be burned at the stake as a witch. Isaac's sister Julia attempts to prevent Hector from killing him right up until the end.

Isaac fights Hector several times over the course of the game, each time with ever greater weaponry and Innocent Devils. The Devil Forger successfully prevents Trevor Belmont from interfering in Dracula's resurrection by attacking him from behind. Isaac is forced to become the new host of Dracula when he fails to trap Hector in his - really Dracula's - plans. He dies in the resulting battle between Hector and Dracula.

The contrast between Isaac and Hector is interesting to see. Isaac seems to be younger than Hector, so it is easy to see how he used to respect him, as is discovered in the course of the game. Their dress style is also very different, as is the color of their hair. Isaac's fiery red hair may be taken as a symbol of hatred and anger, while Hector's white hair may be thought of as a symbol of purity, wisdom and nobility. In short, the opposite of everything Isaac has become. It may also be noted that Hector is a very masculine figure, while Isaac also comes across as sounding and acting somewhat effeminate.

He is something of a tragic character, in spite of his amoral actions and his vengeful, obsessive attitude toward Hector. Hector observes, in the end, that Isaac's insanity and actions were all precipitated by Dracula. Being too far gone in madness and too much possessed by Dracula for anyone to save, Isaac can find peace only in death. Hector, when told by Julia that there is no other way, grants Isaac this in the end.

Trivia

 * Isaac's name functions both as a hint that all isn't quite as it seems with him, and also as a reference to a particular bit of vampire lore. Biblically, Itzhak (Isaac) was the son of Abraham, and almost sacrificed as a test of his father's faith. Unlike his namesake Forgemaster, however, Itzhak survived. The vampire folklore his name references appears in the short story "A Kiss of Judas" by Julian Osgood Field, writing under the pseudonym X.L. A principal character in this story is Isaac Lebedenko, who dies and, when reborn, becomes a type of vampire known as a Child of Judas in order to exact revenge on a deserving enemy. Interestingly enough, Children of Judas are said to have red hair.
 * His Innocent Devil Abel is another hint at Isaac's ultimately-tragic nature, and his end. Abel, Biblically, was the first victim of murder. While Isaac is hardly an innocent man, he is very much a mere pawn in Dracula's game, to be used as a means to a end.
 * His clothing, too, is yet another hint as to his true nature. As pointed out by the games reviewer at Chapel of Resonance, it appears as if Isaac is wearing only the remains of his former uniform. The Prelude of Revenge comic, packaged with the soundtrack sampler CD, uses Isaac's attire as a symbol of his mind unravelling. The madder he gets, the more tattered his clothing gets, until we see him in-game in purely ornamental armour bits and those strange pants. Thanks to Dracula's machinations, Isaac is only broken pieces of the man he once was. Unfortunately, Isaac erroneously blames Hector for the destruction of his life. Curse of Darkness is very liberal with symbolism - not uncommon for IGA, who seems to love his easter eggs.
 * Isaac and Hector together embody the "Red Oni and Blue Oni" trope. Isaac is denoted by red, and is emotional, temperamental, and led by his heart. Hector, in blue, is the more logical and rational of the pair, and is able to think things through, consider what he has been told, and in the end save himself from an extremely bad ending.
 * Isaac bears a resemblance to certain versions of Simon Belmont due to both of them having black clothes and red hair.
 * Isaac in-model game shares the same bone animations of Hector, which means they move exactly the same. Also, Hector can forge both weapons used by Isaac in the two encounters: the Chauve-Souris (the game's most powerful Spear) and the Laser Blade (the game's most powerful long sword).
 * Since his sister is Julia, his family name may be Laforeze.