The rather arbitrary set of spells that can be made permanent always bothered me. Here's a stab at an expanded version.
School universal; Level sorcerer/wizard 5
Casting Time 2 rounds
Components V, S, M (see tables below)
Range see text
Target see text
Duration permanent; see text
Saving Throw none; Spell Resistance no
Permanency increases the duration of other spells. You may use permanency on any spell, subject to the following restrictions:
1) The permanency spell must be cast at a caster level equal to 8 + the spell level of the target spell.
2) You must expend an amount of diamond dust equal to 2,500 * spell level of the target spell.
3) The target spell must have a duration expressed in discreet units of time (including rounds, minutes, hours, days, weeks, or years), or concentration. Permanency also works on any spell containing the word "Symbol" in the spell name, and on the spells Shrink Item, Stolen Light, and Phase Door. Permanency has no effect on spells with a duration of "see text", instantaneous, or permanent, except those allowed in the previous sentence.
Cantrips count as a level 1 spell for both minimum caster level and cost requirements.
SL Cost CL
0 2,500 9
1 2,500 9
2 5,000 10
3 7,500 11
4 10,000 12
5 12,500 13
6 15,000 14
7 17,500 15
8 20,000 16
9 22,500 17
The minimum caster levels and the costs work out identically to the original version.
Limiting the viable target spells by their original duration is meant to reduce shenanigans. For example, True Strike does not work with this version of permanency, because it has a duration of "see text". However, it would work with Bungle, which would be a pretty nasty debuff. Any other shenanigans I'm missing? I didn't attempt to go down the entire list of all pathfinder spells from every book and splatbook.
I've grandfathered in a few spells from the original list that had durations that would otherwise have disqualified them.
While admirable, this really does open up some serious shenanigans. This is something that a DM should buy off on, only on a spell by spell basis.
For example permanancied Haste would only cost 7500. Boots of Speed cost 12,000 and only give you 10 rounds a day (granted, you don't have to worry as much about dispel magic with the boots).
Once we get out of core spells you get even crazier. Pay a wizard to cast tears to wine (aka tears to win) on a barrel of water at caster level 15. Everyone who drinks a sip of it gets +10 on all wis, cha, and int based skill checks, forever. This would only cost 6,200. To buff everyone you wanted, forever. Every perception roll, every knowledge check, UMD roll and much more.
Permanacied spells have an advantage over magic items in that they don't take up a item slot. They have a disadvantage in that they are more vulnerable to being dispelled. Their pricing should be roughly on par with an item that grants a similar bonus. Perhaps due to their vulnerability to dispel they should even get a slight discount. But to use the example of tears to wine above, a +10 to a single skill item would cost 10^2 * 100 = 10,000 gold.
With the permanancied tears to wine, you could give hundreds of people + 10 to a bunch of skills for only 6,200 gold.
This is why each spell should be approved by a GM.
I've always kind of chafed at the small number of spells that can be made permanent. I agree that any other spell should be adjudicated on a case by case basis with the GM.
In fact the spell text even provides for this. :)
The GM may allow other spells to be made permanent.
Yes, Haste occurred to me right after I posted this. And then I thought "Welcome to your permanent -10 penalty on all social skills because you sound like Alvin the Chipmunk. Also you're aging at 4 times the normal rate, and your clothes chafe like the dickens."
But yeah ... the more I look at it, the more this just doesn't work. Too many ways to circumvent the economic system, for one thing. Permanent align weapon so you don't need Holy/Unholy weapons. Permanent Lead Blades would be cheaper than the +1 bonus for an impact weapon.
I guess I'll just have to fall back on telling players that I'm pretty permissive when it comes to Permanency.
This was still a useful exercise. I understand now how they come up with prices and minimum caster levels for the spells that ARE explicitly listed as working with Permanency. Those always seemed pretty arbitrary to me before. It took taking the spell apart completely to see how it works.