What is the Arcane Fusion Trick?

[Saambell]

I've heard mention of it, and looked it up.

ARCANE FUSION
Universal
Level: Sorcerer 5
Components: V, S; see text
Casting Time: 1 standard action
Range: Personal
Target: You
Duration: Instantaneous
You weave two spells together in your
mind and release them in a single burst
of magic.
When you cast this spell, choose any
1st-level sorcerer spell you know and
any 4th-level or lower sorcerer spell
you know. Neither spell chosen can
have a casting time longer than 1 standard
action. Both spells take effect in
the order you choose, as if you had cast
them one after the other using only one
standard action, but you don't expend
any additional spell slots to cast those
spells. Effectively, you cast two other
spells using this spell's 5th-level spell
slot. Each of the chosen spells has its
normal effect, including range, target,
area, duration, saving throw, and spell
resistance as appropriate to the spell's
level.
If either spell requires a material component,
focus, XP cost, or other special
cost, these must be used or paid as part
of the casting of arcane fusion.
It seems pretty clear that Arcane Fusion can't Duplicate itself, so how does it work?

[(Un)Inspired]

Use it to cast celerity then cast arcane fusion again with celerity.

[Kelb_Panthera]

The metamagic feat sanctum spell causes any spell its applied to outside of the designated sacntum to be cast as a spell one level lower than it normally is. By making the 4th level spell that arcane fusion produces a sanctum arcane fusion it creates a recursive loop where by you can produce an arbitrary number of 1st level spells and one 4th level spell for the cost of a single 5th level slot. Note that his only works -outside- the sorcerer's designated sanctum.

Edit: (un)inspired's trick also works if you can get yourself immunity to the daze effect.

[Saambell]

Thanks for explaining.
Was in an argument about if there was a loop. the other guy said they would not design something so broken. I guess this is fallout from different people doing different books and not talking to each other.

[(Un)Inspired]

Thanks for explaining.
the other guy said they would not design something so broken.
Hehehe. Ahhh it's fun to be naive.

[eggynack]

Thanks for explaining.
Was in an argument about if there was a loop. the other guy said they would not design something so broken. I guess this is fallout from different people doing different books and not talking to each other.
Eh, in this case I think it's more about generally unintended consequences. Sanctum spell was clearly intended to provide a spell that's stronger within your sanctum and less strong outside of it. The designers didn't anticipate that the spell level lowering half of the effect would change the game in wacky ways. In other words, I'm pretty sure that the writers of the two books could theoretically have looked at the other's work, and not noticed any wacky interactions.

[Noldo]

The metamagic feat sanctum spell causes any spell its applied to outside of the designated sacntum to be cast as a spell one level lower than it normally is. By making the 4th level spell that arcane fusion produces a sanctum arcane fusion it creates a recursive loop where by you can produce an arbitrary number of 1st level spells and one 4th level spell for the cost of a single 5th level slot. Note that his only works -outside- the sorcerer's designated sanctum.

I see two problems with that trick:
Although Sanctum Arcane Fusion would be cast at effective level of 4 outside the sanctum, I would say that it is highly debatable that Sanctum Arcane Fusion would qualify as 4th level spell known by the sorcerer, since the spell would still require 5th level slot to cast.
Even if one accepts a Sanctum Arcane Fusion as a valid spell for Arcane Fusion, as metamagiced spell with casting time of 1 standard action, a Sanctum Arcane Fusion would have casting time of 1 full round action and thus be invalid target for Arcane Fusion (unless a method to quicken metamagic is applied).

[Kelb_Panthera]

I see two problems with that trick:
Although Sanctum Arcane Fusion would be cast at effective level of 4 outside the sanctum, I would say that it is highly debatable that Sanctum Arcane Fusion would qualify as 4th level spell known by the sorcerer, since the spell would still require 5th level slot to cast.
Even if one accepts a Sanctum Arcane Fusion as a valid spell for Arcane Fusion, as metamagiced spell with casting time of 1 standard action, a Sanctum Arcane Fusion would have casting time of 1 full round action and thus be invalid target for Arcane Fusion (unless a method to quicken metamagic is applied).

The former was the crux of the debate when the trick was first discovered. Ultimately this line
All effects dependent on spell level (including save DCs) are calculated according to the adjusted level. was the key. Arcane fusion is an effect that asks about the spell's level and for effects dependent on level a sanctum arcane fusion is a fourth level spell.

The latter is negligible. Any sorcerer that intends to rely on metamagic will, of course, pick up rapid metamagic at 9 and will often take metamagic specialist in exchange for the familiar at 1.

[Juntao112]

Arcane Fusion specifies that you cat a 4th level spell that you know*, though, and while you know arcane Fusion, you don't know a Sanctum Arcane Fusion...

*I assume know means from your list of sorcerer spells known.

[Kelb_Panthera]

Arcane Fusion specifies that you cat a 4th level spell that you know*, though, and while you know arcane Fusion, you don't know a Sanctum Arcane Fusion...

*I assume know means from your list of sorcerer spells known.

I'm 90%+ sure that that can be worked around too, if necessary. The simplest thing I can think of is arcane preparation. When you have the spell prepared in such a way, and it would be able to bypass the standard action or less clause for arcane fusion this way as well, there's not a very substantive argument that you don't know sanctum arcane fusion.

However, it can be argued that if you know sanctum spell and you know arcane fusion you know sanctum arcane fusion.

[TuggyNE]

Arcane Fusion specifies that you cat a 4th level spell that you know*, though, and while you know arcane Fusion, you don't know a Sanctum Arcane Fusion...

If that fixes the problem, it does so only by ensuring that arcane fusion is useless for applying metamagic spontaneously, which seems rather key to the Sorc concept, and since it's a Sorc-only spell….

[Rubik]

Since the spells called into effect by Arcane Fusion are the ones you cast while casting Arcane Fusion, wouldn't they be affected by any metamagic you apply to the original Arcane Fusion, thereby allowing for Arcane Fusion loops anyway? It's like using an Empower Spell'd Limited Wish to cast Enervation. Even though Empower wouldn't work on the same combo for Polymorph, it would still affect Enervation properly, even though Limited Wish doesn't always benefit from Empower Spell.

[Noldo]

How should any metamagiced spells be considered? For all effective purposes (save DC, globe of invulnerability, etc.) only Heighten Spell changes the level of spell. So should Empowered Magic Missile count as 1st level spell even though it would require 3rd level slot to be cast?

[Rubik]

How should any metamagiced spells be considered? For all effective purposes (save DC, globe of invulnerability, etc.) only Heighten Spell changes the level of spell. So should Empowered Magic Missile count as 1st level spell even though it would require 3rd level slot to be cast?That's exactly it, yes.

Sanctum Spell also explicitly heightens (or lowers) the level of the spell.