Kolthunral is the Netherese flying fortress currently besieging Surcross. We’ll look at it first because it kinda dominates the skyline and its goals are important to contextualize everything else that’s going on in this area.

The arrival of the fortress was a complete surprise even to Szass Tam, who considered the current conflict with the Netherese to be a distant and minor dispute over Shadowfell supply routes way off to the west in Neverwinter.

That conflict is happening because, as we already know, both sides have ongoing plots happening in the Neverwinter area and need a constant influx of material and personnel from home: Valindra’s group is at the Dread Ring, and Clariburnus’ group is at Xinlenal. The Prince of Shade evidently disagreed with the lich about the importance of the dispute and dispatched the fortress to solve it once and for all.

There are many rumors and theories about why Szass Tam hasn’t gotten personally involved in this battle. Some say that if he did it would attract the collective attention of the other Princes of Shade and lead to one of those Realms-scouring epic level wars everyone wants to avoid. Others say he realized all of this is ultimately Valindra’s fault and he wants to see how she gets out of it.

Kolthunral is captained by Duchess Antheriss, one of Prince Caliburnus’ subordinates. She was a shadar-kai in life, and is now a Spirit Devourer.

Construction

Kolthunral uses the same principles as any Netherese flying enclave to stay in the air, with a mythalar and everything. The thing that makes it atypical is that it’s thoroughly militarized. Most of the inhabitants are soldiers, and the rest are only here to work support jobs for the army.

The bottom of the flying island is encased in thick enchanted metal armor, and the city has towers jutting out at all angles (even from the bottom) festooned with siege and anti-air artillery similar to the engines used by Thay to defend its borders.

Spatial Distortions

The interior of the fortress is partly made of shadow-stuff that warps and distorts space, meaning it’s bigger on the inside and can actively misdirect and confuse intruders. The same techniques were used to build its ultimate weapons, the meteor tubes.

Meteor tubes are, well, straight metal tubes that connect the inside of the fortress to circular hatches in its bottom armor. Their enchantments make them “ritual paths” very similar to the Shadowfell Road. You drop a big rock through the entry hole of a meteor tube, and it falls an unfathomable distance through the weirdest and most inhospitable reaches of the Shadowfell, coming out the exit hatch at a speed many times greater than terminal velocity. They’re hard to aim precisely, but the kinetic energy of an impact is so big it can obliterate everything within a few dozen yards.

A meteor salvo could flatten Surcross or Veil if it hit directly, but the cities’ defenses have held so far. Surcross has a force field projected by its five defense towers, and Veil has the Veil of Shadow that gives it its name. This is the main cause of the current protracted siege.

The Prison of Night

Kolthurnal’s prison is a large empty chamber where prisoners are held in place by levitation magic near the center of the space. They’re stuck in place because they’re too far away from the walls to push off, and the magic is too strong to let them move by random thrashing. There’s only the one door, and it’s always guarded, just in case.

This room is reserved for those the Shadovar judge might be useful in a future hostage exchange, which to them means officers or members of “civilized races”. Lower-ranking orcs, gnolls and undead are instead killed outright.

Movement and Power

Kolthunral can fly at a leisurely ten miles per hour, and the only thing limiting its maximum altitude is the fact that it’s not sealed against vacuum. It could easily have flown over the plateau to attack the Thayan heartland, but it’s actual goal is to stop the Thayans from using Shadowfell Road. To do that it needs to destroy Veil and/or Surcross.

The fortress contains doors that are enchanted to become portals to the Shadowfell when it passes over an area where the boundaries are weak. Ironically, this means that it hovers over Veil whenever it needs to take in new supplies.

The city’s mythalar power plant is stored in a nondescript tower near its center. It’s a standard piece of Netherese tech. Destroying it would make the city drop from the sky. There are actually rules for this!

Magical safety measures slow the city’s fall, but its mass is so high they can only do so much, and only for a short time. This gives occupants (and PCs!) time to evacuate, but they’re still in for a bad time if they fail to do so. And you are supposed to give them a good chance to get out - the goal would be to scare them, not force a TPK.

When the city hits the ground, effects depend on what its initial altitude was when it started falling. If it was 100 feet or less, everyone inside takes damage as if they had fallen that distance - the slowed fall speed is counteracted by all the collapsing buildings. If it was higher, everyone inside will be automatically squished.

Impressions

It looks like this region presents the PCs with a sticky situation. Kolthunral’s goals align perfectly with their own, but both factions here are pretty terrible. The group can side with one to defeat the other, but the victor will get a significant boost back in Neverwinter. PCs who don’t want either of them to win will have to defeat them both here in Thay.