Creation and Use of a Magical Focus
A magical focus is an amplifier created by a sorcerer to make casting one specific spell easier for that sorcerer. If a focus is used for any other spell, or by another magician, its usefulness will be diminished or destroyed. Note: these rules are different from those presented in the Book of Sigils, page 128.
A focus may be made out of any material, non-living object. However, crystal, silver, and gold are the best conductors of magical energy; iron and (heaven forbid) star iron make poor foci.
Cast the spell Create Focus (6 ♦) with Definitions (typically totalling 12 points for a quick and easy focus). This part of the process takes only as long as gathering the thaumic energy requires.
Cast the desired subject spell, with all definitions, starting before the expiration of the Create Focus spell. Note that when casting the spell with the completed focus, lesser categories of definition are also included (shorter ranges, for example). This step also takes only as long as gathering the thaumic energy requires. Note that the spell does not actually "go off" -- unless a joker or other unfortunate circumstance occurs; it is merely incorporated into the structure of the focus.
Invest the focus with thaumic energy, starting immediately after (or during) the subject spell. The sorcerer pulls cards at the rate of one per four hours (if of Good Ability - faster for higher ability). While the process does not require that the cards be of the correct alignment, or even the same alignment, in almost all cases they are so chosen.
Good sorcerers may invest two cards in the focus; Great sorcerers, three cards; Exceptional sorcerers, four cards; and Extraordinary sorcerers, five cards. The maximum total face value of the cards in the focus (of all suits) is equal to the sorcerer’s Ability rating.
If a focus is used repeatedly, it can gain in power. For every 10 years of use, add 1 to the thaumic energy rating of the focus (in the suit of the spell used). The maximum thaumic energy rating for a focus is 14.
When used by its creator, for the spell it was created for, the focus adds its thaumic value to the caster’s. It has the energy and alignment of its contained cards. The caster must see and touch it to draw upon its power. Only one focus can be used by a magician in the casting of a spell.
If used by the caster for any other spells, or by any other sorcerer at all, the focus is unraveled by the amount drawn upon, leaving behind a lesser (or extinguished) focus.
As long as a focus has at least one point of thaumic energy still invested in it, it counts as a magical object.
See page 205 of Castle Falkenstein. An artefact is in many ways an improved focus. They have a face value, and are aligned to one or more aspects (card suits, that is) -- or, rarely, to all aspects. They can be used for any spell; if used as an unaligned aspect ("out of suit") they only add 1 thaum, and present the usual problems with using unaligned power. Again, they can be made from any material, non-living item. Gold, silver and crystal are preferred (although having no actual game effect); iron or star iron won't do.
Artefacts don't care who uses them, and are not unraveled by normal use ... but anything with thaumic energy bound into it can be unravelled. Unravelling an artefact reduces its face value by the amount of thaumic energy produced; the aspect of the energy is whatever is usual for the artefact. So, in essence, you can get twice the normal face value of power from an artefact, if you're willing to use it and then unravel it.
Example: Nimue's Staff is a gnarled wooden stick, carved with intricate Celtic designs; it is aspected to Diamonds, with the face value of 10. A Masonic sorcerer, in combat with an evil being, is casting Alchemic Destruction; the Staff provides 10 thaums towards the spell casting. But that's not enough -- even after unravelling himself a bit, he's 6 points short! Desperate to destroy the being, and unwilling to take the time to gather more thaumic energy (i.e., draw more cards), the sorcerer unravels 6 points from the Staff, and casts the spell. The Staff now has a face value of 4, which may gradually recover over hundreds of years.
Unravelling artefacts is considered quite unprofessional by sorcerers -- or at least an act of utter desperation.