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Old 05-04-2015, 09:01 PM   #35
Grouchy Chris
 
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Join Date: Nov 2007
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Default Re: Building permanent magical traps with GURPS Magic

So it turns out that "always on" does not work for items that cast area spells in the way I thought it did at all. Apparently I need to go back and think about it some more. Here's what Kromm had to say:

Quote:
Originally Posted by Kromm, in an email
> (1) If a magic items enchanted with an area spell (a ring of Fire
> Cloud, let's say) also has a Power enchantment of sufficient level,
> does it count as an "always on" item, allowing for the creation of a
> Fire Cloud spell that lasts until the ring is removed by the caster?

Items can be truly "always on" only if their Power enchantment will
cover all possible costs. If there's an open-ended range of costs -- as
for an Area spell -- then a given casting might endure indefinitely as
long the caster is awake, but the item per se isn't "always on."

> (2) If "yes" on (1), is the spell eligible for use with the Link
> spell? (The text for Link stipulates that cost reductions for high
> skill do not apply, making indefinite maintenance of a spell at zero
> cost impossible by direct casting, but the issue of casting via
> Powered magic item is what I'm wondering about.)

Well, the answer to (1) is "no" . . . but note that Link works *very*
differently for enchantments. In that event, Link isn't ever actually
cast by the item, making the issue of its energy cost irrelevant. For
enchanted items, Link simply controls operation.

> (3) If "yes" on (1) and (2), does the use of the Link spell mean
> that when the Fire Cloud is triggered, it persists indefinitely
> without regard to whether or not the caster removes the ring?

Again, given the previous answers, this is almost irrelevant, but . . .
Taking off a worn item ends the spell. It has to be worn to work, even
if it costs no energy to use. "Always on" items are by definition only
"always on while used in the prescribed manner." For worn items, that
means "while worn."

> (4) If "yes" on (1) and (2) but "no" on (3), what controls the
> duration of the Linked, item-cast Fire Cloud?

Someone with an item that has Fire Cloud, high Power, and Link can cast
a free-to-maintain Fire Cloud as long as the conditions of the Link are
met. However, as Power spells out clearly, the user still has to remain
awake -- and as I just said, taking the item off would end the spell.
So the practical limit on duration is the length of time the user can
remain awake while wearing the item.
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