metamagic shenanigans, darkness edition

Permanent and instantaneous spells. I'm gonna look through the metamagics for horrible things, just in case there's shenanigans to be had here.

 At a glance:
Any permanent light spell, such as Continual Flame, can become a Solar Spell. This seems to be more or less intended, since there are different rules for different durations, and instantaneous and permanent are both called out.

Eclipsed Spell seems to possibly work to turn a light spell into a dark spell. I see no indication it changes the descriptor (thank goodness), but if you want your permanent dark spells, if I'm reading this correctly you finally have it. Amusingly enough, this doesn't seem to be compatible with Solar Spell, since Solar Spell can only be applied to spells with the Light descriptor (which this doesn't remove), but is also actually contingent on raising the light levels for non-damaging effects. So you can't use a Continual Light spell both to darken its area and to dazzle opponents.

Umbral Spell changes the descriptor to Darkness. "You cannot use this feat on a spell with an instantaneous duration or a spell that does not target a creature or object." I see no reason it can't be applied to a Light spell of some stripe; it creates a 10 foot spread of darkness, which could be pretty darn amusing with a spell of Continual Flame. It won't work on Wall Of Stone or Consecrate, since these are instantaneous spells, but Bestow Curse or Blindness seem to be compatible. Indeed, Arcane Mark and Arcane Lock would be awfully amusing ways to use this metamagic feat, since they'd advertise themselves quite prettily.

Now, Eclisped Spell specifies it works on spells which create light or dark. I'm not sure if Umbral Spell on a spell that does not usually produce dark or light counts. That might be down to DM caveat, and I'd be on the fence about it; it's a lot of feats for a very silly idea, but it's harmless fun as far as I can tell.

Things get a little... stranger with Shadow Grasp.
Let's try this out. You use Continual Flame because it's Permanent. But you apply Eclipsed Spell to exchange its light for dark, because why not. Then you add Umbral Spell, creating a 10' area of rather spectacular shadow in the middle, also adding the descriptor Darkness. Having done that, and I'm pretty sure it now has both Darkness and Light descriptors regardless of what you're really intending, you then apply Shadow Grasp. The three together come out to a +3 spell level. (Shadow Grasp does not seem to specifically state you can't use it on a Light spell, only that it requires the Darkness descriptor, and Umbral Spell is a prerequisite; I'm quite certain they're intended to be useful together.) Those who enter the area must save/SR or be entangled while in it, and for a round after leaving.
You could also probably skip the Eclipsed Spell and go for a light source that also have 10' of shadow in the middle, and throughout the entire area I'm pretty sure you'd be entangled.

Umbral Spell would also work with Blindness/Deafness, if you're feeling kinky.

 I'm looking at a few other spells as I type this. Some of these are kinda hilarious.

Glyph of Warding, and probably any Glyph spell, has an area as possible Target/Area functions, if you decide you want that instead of Object Touched. It's Permanent Until Discharged (and dismissible), so the interaction with Shadow Grasp would probably be sort of entertaining. If all you want to do is warn people "don't screw with this thing," though, you could do worse than applying Umbral Spell.

Lissalan Snake Sigil gives two different durations. It doesn't target an area, so no Shadow Grasp for you, but for the duration of its triggered effect (permanent until discharged, then 1 day/level), you can have them walking around in a 10' shadowy haze. That's just *fun.* Also, the other effects are neat.

Stolen Light, a spell that makes a photograph in a spendy gem, gets odd. Permanent until used, as far as I can tell, or at a cost of 5k and the Permanency spell (at 10th level) it can be made actually permanent-permanent, able to do its thing again and again. No area, so no shadow grasp. There's actually specific information about light sources captured in the photograph being within reasonable ranges, which appears to have nothing to do with anything else involved at all. See if you can Eclipse Spell and have your DM allow you to take a photograph in in the negative. ^_^

Transmute Mud to Rock!
Tired of folks coming through your walls or floor? Make 10' cubes of Rock out of an equal volume of mud! These are an area, so the rock in question can Shadow Grasp. This requires the spell be given the Darkness descriptor, requiring Umbral Spell. It's soft stone, such as sandstone, but attempting to emerge from it will be complicated, as it will entangle those passing through it. And I see nothing indicating who it wouldn't work on.

Transmute Rock to Mud!
Pretty similar, but probably effectively temporary. A rather more tactical and immediate spell, you can use this to mess with folks pretty well. Follow it up with Transmute Mud to Rock, and... well.

Forbiddance!
60' cube per level area, permanent. Messes with folks of opposing alignment, and restricts planar travel. Honestly, at that point entangling those inside is just thematically appropriate.