He flies through the open set of doors at the front of the temple.

The Temple of Asmodeus is full of powerful devils and priests and other horrors.

Not a single one of them can detect an invisible creature under mind blank that's also incorporeal. Visual senses cannot detect invisible creatures. Nonvisual senses cannot detect incorporeal creatures. True seeing fails against mind blank.

He already knows the way to Ignasi Arabasti's private living space.

The forbiddance—

—stops ethereal creatures, not incorporeal creatures. Very different. He's lawful neutral and quite powerful besides. It stings him a little.

Ignasi is seated on a couch having a conversation with a cleric of Asmodeus.

Trap the soul.

Ignasi disappears. The cleric and the guard devils turn—

Contingent action triggers the moment trap the soul resolves.

Toff is under both haste and fly. He passes through the walls and out the temple before anyone can move. He sends a phrase over a telepathic bond.

In addition to her permanent demiplanes, Felandriel maintains a number of temporary demiplanes for a variety of purposes. She extends them with collaborative thaumaturgy from Gallipsiwhoop and renews their duration when they're close to expiring.

Demiplanes can often have very exotic properties. Consider the walls and ceiling. They aren't made of anything. Space itself simply ends. They have no physical properties but otherwise interact with matter and energy normally. This produces a strange kind of reflective surface that otherwise essentially doesn't exist.

This demiplane is a small rectangular tube. Twenty feet tall, ten feet wide, ten feet long. There is no gravity here. The vast majority of the space within the demiplane is filled with black powder. Felandriel transmuted it into existence using grand polymorph.

Gate.

A magic mouth triggers in response to the gate. A tiny poppet hears the magical speech and throws a vial of alchemist's fire.

One hundred thousand pounds of black powder ignite, starting from the top. Black powder is very inefficient at producing energy. It typically deflagrates instead of detonating. Much energy is lost to heat and light and friction. It doesn't matter. In this scenario, it might as well be a high explosive. All of the energy is reflected back off the walls. The explosion has nowhere to go but down. Within a fraction of a second, it exits the demiplane through the gate.

A cylinder of blinding fire tears through the air at over three times the speed of sound. It carves into the ceiling and the floor and tunnels deep into the earth. Every human within the temple except for the archbishop is instantly vaporized. All of their magic items are destroyed. The lesser devils are slain by the shockwave.

The Temple of Asmodeus is now a molten crater. The air within it is hot enough to melt steel. The air surrounding it is hot enough to evaporate water into steam. Adjacent buildings have been reduced to flaming rubble.

Every window within a hundred meters shatters instantly. The sky seems to ripple as the blast wave tears through the city. Shrapnel is flung across the street.

Incorporeal creatures are immune to nonmagical damage.

That was rather larger than I was expecting. Dozens of civilians are dead, at minimum.

Felandriel is also incorporeal.

I can do much bigger, if you want. The explosion was also larger than she was expecting. It's a very good thing she didn't use an even bigger one.

Not anywhere near the city. Why is a chaotic good elf so similar to his great grandfather. Is a love for catastrophic explosions really the uniting factor between lawful evil and chaotic good?

Tencednil sees a terrible flash in the sky. A wave of air almost knocks her off her feet entirely. Windows in the buildings near her crack.

What was that. It's starting.

From where she is, is towards the Citadel towards the flash or away from it?

Towards the Citadel is away from the flash. It came from somewhere up in Citadel Crest.

And it came from the sky, and left that much of a shock. It must have been targeted at something on the ground. Nobody wants Korvosa destroyed, which means someone has a way to make a giant super-powered Flame Strike or an explosion large enough to be seen in the sky. How... Not important right now.

"We need to get to the other guards! Somewhere needs us, and it's not here!" Her spider... doesn't seem substantially changed. It must have been inside. She doesn't need to leave immediately, then, but she should still try to angle towards the Bank to be close to Mother when she does.

The captain shakes himself a bit. "We push forward! There's an emergency muster point in that direction!"

Going towards the explosion? Really? ...right. Guards. This is what they're paid for. To walk straight into what is, with luck, just an archmage ambush rather than an archmage duel, and will therefore involve only the wreckage of whatever happened without risk of it happening again while they're in the area. Hopefully.

Well, she hasn't been called. Forward it is.