Something I've been kicking around. Comments welcome, and if anyone at Catalyst wishes to introduce something like this officially, feel free, just give me a bit of credit, yeah?
In the Fourth World, magicians originally cast their spells by taking raw mana, and shaping it with their will alone into the shape of spells. Later, as the great Enemy began to enter our plane, magicians found that doing this drew the enemy's attention. They began to create 'filters', allowing them to use the magic at one step removed from the astral, and hide their presence.
When the Fourth World ended, and magic faded from the world, this art was forgotten, and many items of great power were lost to the ravages of time. However, artifacts found in the Deep Lacuna beneath LA have brought this practice to light once again, though the reasons for it remain shrouded in mystery, known only by a few. Most who know of these filters simply believe them a means for the magician using them to expand their repertoire.
A Spell Matrix item can be any item that is crafted in some way, and can be carried. Weapons, clothing, and jewelry are the most common, though other forms are possible. A spell matrix item holds a spell at certain Force. A character bonded with the item can use the spell at that Force, using their own Spellcasting skill, and resisting Drain (with any appropriate bonuses from Centering or other abilities) and sustaining penalties as normal. However, it allows the user to cast the spell, even if it is not on their list of known spells. A Spell Matrix Item can be enchanted by any character with the Enchanting skill and the Quickening metamagic.
Example: "Lightning Blade" - Electric Aura, Force 5 (limited to self only). When activating this blade's ability, the caster resists 3 Drain. Whether the Drain is Physical or Stun depends on the caster's Magic score. The DV of the caster's melee attacks are increased by the number of hits on the Spellcasting test, and the attacks deal Electric damage and are resisted by half Impact armor (+Nonconductivity). Someone who successfully physically attacks the user in melee must resist 5P(e) damage. The caster takes a -2 penalty on all tests while sustaining this spell.
Example: "Rei Gun" - Manabolt, Force 6. Whimsically named after a character's ability from an old anime, this pistol contains a Manabolt spell. When activating this weapon's ability, the caster resists 3 Drain. Whether the Drain is Physical or Stun depends on the caster's Magic score. The target takes 6P+net hits damage, resisted as normal.
Example: "Wizard's Cloak" - Armor, Force 4 (limited to self only); Astral Armor, Force 4 (limited to self only); Levitate, Force 5. When casting one of the spells from this old-style cloak, he resists 3, 2, or 3 Drain, respectively. Whether the Drain is Physical or Stun depends on the caster's Magic score. The actual effect is based on the results of the caster's Spellcasting test, as normal. The caster takes a -2 penalty on all tests while sustaining each of these spells.
Example: "Hat of Disguise" - Physical Mask (limited to self only), Force 4. When casting the spell from this hat, the caster resists 1 Drain. Whether the Drain is Physical or Stun depends on the caster's Magic score. He takes a -2 penalty on all tests while sustaining this spell.
Example: "Ninja Suit" - Improved Invisibility (limited to self only), Force 5; Stealth (limited to self only), Force 5. When casting either spell from this bodysuit, the caster resists 1 Drain. Whether the Drain is Physical or Stun depends on the caster's Magic score. The effect of either spell depends on the hits on the caster's Spellcasting test. He takes a -2 penalty on all tests while sustaining this spell.
To bond with a Spell Matrix item, one must spend 1 Karma per spell contained in the matrix. Spell Matrix Items cost 2500xForce nuyen per spell contained in the matrix, and have an availability modifier of +(Total force of all spells contained in Matrix). The character must have the matrix item on his person to cast or sustain a spell in this manner, though it need not be in hand to sustain spells. The item must be held in the caster's hand (or worn, in the case of clothing/armor) to cast one of the spells contained within it. If the item is bound to a new character or destroyed, the character can no longer use any of the spells contained within, and they do not regain the karma initially spent to bond with the item. Spell Matrix Items can also be enchanted as foci (and must be bonded as such separately), but the effects of a Spell Matrix Item are incompatible with the effects of foci unless they are part of the same item. However, the focus effects of a spell matrix item enchanted as a focus function normally. In other words, a hat conferring Increase Charisma 3 cannot be used with an external Sustaining focus, but if the hat is also enchanted as a Sustaining focus of Force 3 or higher, it could be sustained through the focus.