Callum Finn

Callum is one of the original "Experimentals" that were created by Silviu prior to the creation of the Balefire Revenants.

He is actually the very first attempt made by Silviu to create an "undead weapon". Unlike the others that are like him, Callum was not given the ability to possess a second soul. His ability to shift instead comes from the fact that he was corrupted into a wendigo before dying, while the "soul hijacking" performed by the others took place after their deaths.

Since he is the first attempt at creating such a weapon, he is riddled with functional issues, including the corruption's tendency to take over his judgment, or cause him to feel ill when it is not actively making decisions for him.

Personality
Callum is shy and prefers to keep to himself, though this is possibly just a side effect of being sickly and frail even in his afterlife. Though he is capable of offensive magic, he avoids confrontations; his health would likely just cause him to crumble under pressure.

Hemoturgy (Slayer variant)
Innately capable of blood magic, in a form that can be used offensively. This is a drastic difference from the Healer variant, which cannot be used offensively on its own. Despite having no differences in mana between the two variants, Callum does not know how to use Healer variant hemoturgy.

Wendigo Shift
Capable of shifting instantly into a wendigo. Unlike the other ghosts, Callum is not capable of using hemoturgy or Phantom Phase skills while shifted.

Phantom Phase
Callum is capable of making himself incorporeal to perform a number of tasks. While incorporeal, Callum cannot use hemoturgy or Wendigo Shift.