"I need to explain magic before I go on. Some of the weapons in the game are magic-based, like the Voodoo Doll and the Decapitator. These weapons use magic ammo called Focus. Focus is not picked up in the levels, but rather is regenerated with time. The regeneration rate and upper limit for how much Focus you can have is defined by your magic attribute."
--James Wilson III
Focus is the term given to magic power in Blood II: The Chosen.
Focus works much like ammo for magic weapons, such as the Life Leech, Voodoo Doll, and The Orb, but instead of finding ammo caches to resupply, focus regenerates over a period of time. The regeneration rate and capacity of Focus differs with each character.
Each character has a certain amount of magic power. Ishmael has the most, with 400. Ophelia has 300. Caleb and Gabriella have the least with 100. These differences are not particularly noticed unless using the characters in BloodBath or The Nightmare Levels. In fact, many people who only played the single-player campaign of Blood II thought The Orb had no alt-fire, since it takes 200 focus, twice Caleb's maximum amount.
Certain modifications, such as Extra Crispy, change the default focus given to characters. This allows Caleb, for instance, to make a much greater use of focus based weapons. The Focus power can also be adjusted from the base character defaults in Bloodbath, and this was originally intended to be possible for single player games as well.