It's clear that mages can use Sustaining Focus for their own buffs.
What, if anything, stops the spell?
If the mage goes unconscious, or takes a nap?

I vaguely recall text in RAW limiting Adepts bonding foci other than Weapon Foci, but I can't find it.
Adept A bonds a F4 Sustaining Focus.
Mage B casts Increase Reflexes (at F4) on Adept A.
Can they use the Focus to sustain the spell?
Does the spell still have an astral link to Mage B, does it stop if he dies?
Can Adept A de-activate the focus (to use some other focus), then re-activate it and get the spell effects again?

Could an otherwise mundane person use a Knack to bond a weapon focus?

Alternate scenario: Susan the shaman bonds a Sustaining Focus (Detection) in the form of a ring, then casts Detect Soy and sustains it through that focus. As long as Susan wears the ring, she can detect soy. What if Joe takes the ring and spends Karma to bond it as his own Focus? Does Joe now have a Ring of Soy Detection? Or does the sustained spell get removed from the focus during the process of bonding to the new owner?

Pretty sure the focus can only be bound to one individual at once and foci aren't like DnD Rings of Spell Storing... well Anchoring foci kinda are, but lets not go there... A spell is cast into the focus and the focus takes over the distracting activity of sustaining the spell. Instead of having to concentrate to maintain the shape of the mana you manipulated you pass it off to your sustaining foci. Kind of like if you blow up a balloon with an irregulaely shaped end. You can't tie it off to itself because of it's shape, but if you had an object of the perfect size and shape it could plug the open areas and you could tie it off around that object( Foci of appropriate force and category) Since this balloon is linked in a fundamental way to you, if you pass off the plugging object to someone else it can't go with it and if you don't start plugging the holes yourself it deflates and is of no use to anyone.



So... yeah, no you can't pass off spells like that. Quickened is what you are looking for.

Chris

A sustaining focus sustains a spell. It does not contain a spell. If the binding mage dies, a focus is unbound and can no longer do its function. If the caster gives away the focus, it is deactivated and the spell fades away. The caster does not even get the chance to change the target of the spell, unless that is allowed by the spell description. All a sustaining focus does is removing the -2 distraction penalty. Nothing else.

Sure Fortune, 191. "The number of foci you can have active at one time is equal to your Logic." Since whatever it is that gave the mage's body a logic is gone (spirit, astral form, who knows) then the mage's body no longer has any mental stats, and thusly can't have any active foci.

Alternatively, I don't think the mage's body has a Magic rating either, which means that the magician can't have more foci bound than his magic rating.

This would be feasible though...

Adept power Living Focus (Street Magic, 1 Power Point)
Adept bonded to Sustaining Focus

Mage casts Spell upon Adept
Adept Sustains himself (Living Focus)
Adept shifts the sustaining to his Sustaining Focus

It costs you an adept power, but if you regularly work in tandem with a mage the mage might be very appreciative to have help with sustaining multiple spells.

@Tarantula: Reaching, but I guess that's good enough.

Of course, Wards would be another matter. They wouldn't necessarily drop with the death of their creator, would they?

Indeed. Much as a mage can't cast a spell, bond a sustaining focus, and then put the spell in the focus. You cast the spell THROUGH the focus, and it goes in, not after the fact.

The adept could bond it, if he really wanted to waste his karma like that. But it would be of no use to him, since he can't cast a spell, and thusly, can't ever have his spell cast through his foci.

Wards: Right, they last for weeks determined upon creation. Creator death doesn't matter.

Ahh.. guess I had missed the cast through the focus. I was thinking it worked much like spirits sustaining something for you. At least I don't think you have to cast through them do you?

@Fortune: I admit the reasoning is reaching, but I indeed meant the second part Tarantula cited. No magic attribute = no bound focus, focus not bound = focus not useable.

@Nightwalker: You can even summon the spirit after you cast the spell, no problem. The length of those services often gurantees that you will get the spell back for sustaining...

Ugh. Then no, adepts can't bond a centering foci to aid their centering tests. So, adepts can only use weapon foci, ever. I hate that.

Also, it means any of the various knack type quality magicians can't ever bond any foci at all.

(Except for the astral sight one, which explicitly allows weapon foci to be bound)

Note the section, which is specifically for starting characters.

Knacks have always been a canon problem, because they break the rules in a number of ways.

I agree that I think the sentence was placed in the wrong section. Though, if you want to go that strictly, then while the bonding rules are worded such that the "owner" can bond it (as long as they spend karma and participate in a magical ritual), which means really that anyone can bond a focus as long as they have the karma.

Though, specific foci limit the users. Spell foci explicitly state "empower a magician's Sorcery skills." Spirit foci state "empower a magician's Conjuring skills." While weapon foci state "add magical power to an Awakened character's melee attacks."

Thusly, while anyone can bond anything, only magicians can use spell or spirit foci, and anyone awakened can use weapon foci.

I supplied an applicable one earlier ...

A Power Focus doesn't actually add directly to the Magic Rating. When active, it applies its rating to any tests that involve the Magic Attribute itself.

I wonder what the words 'As with all types of foci' actually mean then.

Not contact with the target of the spell, that was sr3 and earlier. In sr4 the sustaining focus must remain in contact with the mage who bonded it (opening the question of what happens when the target of a spell your focus is sustaining is another person and they pass through a ward.)

Though yes, the spell would end as soon as the ring left her finger because the focus would deactivate.