Can I place a metamagic'd spell into a glyph of warding? For example, could I use 4th-level glyph of warding to store a safeguarded fireball? Even with the metamagic action cost it still meets the 3-action or less requirement. That way, if the spell triggers whilst I'm nearby (such as if I were protecting my belt pouch from thieves), I'll be unharmed by the blast.
If this would not work, please explain why you think it so.
We'll need the metaphysical interpretation of what Metamagic means:
Does its action become part of the spell's actions, therefore part of the spell itself?
Or is it too separate, a floating "boost" the the caster then imbues into their next spell?
But even if a boost, wouldn't that boosted version of the spell be the one implanted into the Glyph?
I think the last interpretation works fine because Glyph uses the wording that "...you also Cast a Spell..." so there is the opportunity to put metamagic on that spell as you cast it. It's not an uncast spell shifted from the caster into the Glyph's battery. The caster's casting it, giving an opportunity to put metamagic on the spell as they do so, and that's what gets stored.
Unless there are some unforeseen balance/verisimilitude issues, I'd say it's okay.
Would some metamagic options change the level of some Glyph traps?
Would some metamagic options change the level of some Glyph traps?
Not that I'm aware of. Closest thing I can think of are some of the polymorph feats that say to treat your polymorph spell as 2 levels lower for certain purposes.
And then there's Dangerous Sorcery and other abilities that alter the spell at casting. Would those alterations be stored too?
Can I place a metamagic'd spell into a glyph of warding? For example, could I use 4th-level glyph of warding to store a safeguarded fireball? Even with the metamagic action cost it still meets the 3-action or less requirement. That way, if the spell triggers whilst I'm nearby (such as if I were protecting my belt pouch from thieves), I'll be unharmed by the blast.
If this would not work, please explain why you think it so.
No, you can't. If you use a metamagic action, it will apply to your Casting of Glyph of Warding as it's the first casting you do. You would need a way to apply a metamagic to a spell without taking the metamagic action.
And Dangerous Sorcery and any feat you have should apply to the spell inside. Everything that applies to the spell at the moment you cast it should apply to the spell at the moment it is released.
I disagree. The Glyph spell has a 10-minute casting time and says "While Casting this Spell, you also Cast a Spell of a lower spell level to store in the glyph." So if you wanted to apply metamagic to the secondary spell rather than Glyph, you would start casting Glyph, then take your metamagic action just before casting your secondary spell.
You can't intertwine action in the middle of a spell casting.
You cast a second spell while casting Glyph of Warding only because Glyph of Warding states that you cast a spell while casting it: "While Casting this Spell, you also Cast a Spell of a lower spell level to store in the glyph." If you take any other action during your casting of Glyph of Warding, your casting of Glyph of Warding fizzles. You can't Strike, Stride or use a metamagic feat while casting Glyph of Warding. And as such you can't use a metamagic feat on the spell you cast unless you find a way to do it without spending an action.
Good point re: timing, SuperBidi.
In the middle of casting Glyph, it allows you to cast another spell, and that's it. It doesn't allow for a metamagic action, even if Glyph does allow for spells with more action cost.
So hypothetically the Glyph could hold all of a spell's boosted effects, it's just there's no way to do a metamagic boost during the Glyph's casting to charge up the spell. So would that mean a metamagic action without an action cost might work? Ex. A free-action metamagic triggered by the casting of the spell to be included in the Glyph. I'd think so, yet arguably that could disturb the Glyph's casting too.
You can use free actions and reactions in the middle of an action if they have a trigger. Otherwise, I don't think so.