(If you like, perhaps you could sketch up a picture?)
Among all the planes' weapons of war, one of the most forsaken, forgotten, and feared is the skycraft known as Hallowbane. It is a masterpiece, born from the depths of the Plane of Shadows to serve some diabolic lord in ages long since passed. Since those dark spirited times, the skyship has traversed all corners of the planes, and has even been rumored to cross over into the Far Realms where it may pick up the horrors that maintain its magic-infused machinery and pilot it into battle. The devastation this unexpected threat poses is beyond belief and it boasts an arsenal of strange powers and tactics to unleash the abominable tempest that first cast it from the darkened landscape of endless shade.
Hallowbane is run by a captain who runs over its crew with power only surpassed by the titan that houses them all. The position of captain has changed many times, given over as spoils to fiends of greater and greater power.
The ship looks much like one of the oceans, but it bears a skeletal impression as rib-like ridges connect to a massive figurehead. The figurehead will change to reflect the native appearance of its current captain. Eight long landing and support spines run along its keel and are positioned next to barrage cannons. The sight of this behemoth invokes dread on all who confront it. Inside, Hallowbane is wreathed in nigh impenetrable darkness.
Weapons (Special Attacks):
As per its current movement mode (see Creature-like Statistics), Hallowbane may take a certain number of attacks per round. Some attacks require time to recharge or a specific part of the ship to be intact. The DC of any spell effects is 15 + spell level, unless noted otherwise.
Main Cannon (3 attacks, Figurehead intact): The figurehead of Hallowbane contains its most devastating weapon. This main cannon channels the raw fury of the Plane of Shadow into a beam of obliteration. It takes two rounds to charge the main cannon and another to fire, taking three attacks each turn. The cannon fires a 600 foot line of ethereal shadow energy ten feet wide. Once fired, it takes 1d3+2 minutes to recharge the weapon. This energy penetrates all obstructions except walls of force and prismatic walls/spheres. A DC 25 Reflex save allows a creature aware of the beam to dodge it, but anything caught unaware is at the beam's mercy. Anything caught in the beam (creatures, objects, and terrain) is subjected to a CL 18 disintegrate effect. Structural failure can result from this, causing buildings and mountains alike to collapse. Living creatures slain by this attack arise as allips 1d3 rounds later. These creatures ignore the ship and crew, but spread chaos across the remaining landscape.
Heavy Barrage (1 attack, 1+ Spine intact): Below each spine is a magic-based cannon, which functions much like a very powerful, very large wand. It may barrage targets directly below the ship and away to an angle of 60 degrees with two corrupted fireballs (CL 10, 50% negative energy damage). The areas of effect cannot overlap, due to restrictions in the angles of the guns.
Mass Barrage (1 attack, 1+ Spine intact): All along the sides of Hallowbane are small firing ports for launching volleys of blasts. These shots can target anything outside the range of the heavy barrage up to the ship's height (60 to 90 degrees away from a line directly below the ship). For every intact Spine, one bolt is fired per attack (+10 ranged magic attack, dealing 1d6+1 damage, with a range of 500 feet). Only a maximum of half the bolts may be aimed at one target.
Flak Burst (1 attack): This is the ship's only fixed weapon against anything that would dare fly over it. Once activated, it reproduces the effect of meteor swarm with a single meteor (CL 18). This projectile flies straight up, impacting one target with a successful +15 ranged touch attack. As an alternative, 3 attacks can be spent to fire four meteors.
Aerie of Souls (2 attacks): Two large docking bays line the sides of Hallowbane, covered by wing-like flaps that open up during combat to unleash a wave of sinister creatures upon those nearby. Each side releases a cadre of shadows for a total of 4d4 shadows. This is typically used when buzzing fortified positions or to take the heat off of the ship for a moment. They are loyal to the ship and its crew, but are not under the control of the captain.
Standard Maneuvers (1 attack, once per round, Figurehead intact): Overrun (deals an additional 8d6 damage), bull rush (deals an additional 5d6). Multiple creatures adjacent to the ship can be affected.
Ram (only attack this round, even if in Pursuit speed): If Hallowbane moves at least half its speed allotment this round, it may ram something of at least Gargantuan size that it moves into contact with. It deals 20d6 damage to the target and itself (spread among its remaining parts as the DM chooses). If the figurehead is intact, it may reroll the damage dealt and take the higher outcome of the two and (whether it rerolls or not) only deals half damage to itself. The ship may ram vertically as well (but the figurehead has no effect); ramming up deals damage directly to the hull while ramming down deals damage directly to the Spines (spread across the remaining spines as the DM chooses or the hull if none remain). Damage dealt in a ram is treated as adamantine for the purpose of overcoming the damage reduction of buildings and fortified enemies.
Repairs (only action this turn): Hallowbane regains 10 hitpoints to each location. Any surface wounds and gaping holes are cosmetically repaired along the outside of the hull, but not on the inside. Parts cannot be replaced once destroyed, but require a trip to unknown parts of the Plane of Shadow.
Innate Properties (Passive Abilities and SLA):
Multiplanar (Su): No one can enter or exit the ship via extraplanar means, as it shares a strange bond with the Astral, Ethereal, and Shadow Planes.
Selective Gravity (Su): Hallowbane can manipulate local gravity, allowing it to perform rolls and fly upside-down without impairing those inside. This is also an opportunity to realign weapons into a better position (or even unleash a Flak Burst towards the ground).
Soar Beyond the Sun (Su): Only the crew of Hallowbane can see within its many corridors. There is a constant deeper darkness effect within the ship, which only loyal crew members can see through. Spells of the [Light] descriptor deal damage to the hull when cast inside the ship. Any non-magical light is immediately extinguished. Undead gain a +4 bonus to turn resistance in this darkness. The area of this darkness bestows a non-detection effect, which cannot be denied.
Heart of the Captain (Su): While the captain of Hallowbane is on board, it may use the captain's saves in place of its own, if they are higher. The captain is immune to mind-affecting effects and guides the ship with his or her own natural sanity (or lack thereof).
Panoramic Vision (Su): Pilots and the captain of Hallowbane are granted sight from every point on the hull of the ship, allowing them to see from all angles with their own sight abilities. The ship cannot be flat-footed, unless grounded.
Spellwarding (Su): During each round, the ship may rebound up to fifteen spell levels of enemy spells that enter within fifty feet of the hull. There is a 25% chance the effect strikes its caster, otherwise the effect bounces off without incident. Spells cast within fifty feet are unaffected; only enemy area of effect and targeted spells are intercepted (those with the intent to cause damage to crew or ship, or incapacitate/impair them somehow).
Spell Channeling (Su): Casters within the ship may touch any part of the ship and cast a spell/mystery, or use an SLA through a spine (if any are intact), as if they had casted them from the tip of the spine.
Shadowcasting Focus: Those capable of casting mysteries can cast Apprentice-level mysteries for free while inside the darkness of Hallowbane.
Spell-like Abilities (activated by captain):Planeshift, once per hour. Shadow walk, as full-round action (shunted only 1d10x50 feet). Ethereal jaunt, once every five minutes for as long as desired. Transportation effects affect all within twenty feet of the ship, enemy or not.
Hallowbane is made of ten parts, each with its own HP and defensive values. When the hull is destroyed, the entire ship is defeated.
Hull: The body of the ship.
-Damage Reduction: 20/magic and piercing
-Spell Resistance: 30
Spikes (8): Twenty-foot long spines reinforced to land on, also serve as supports for the magic-based cannons located within.
-Damage Reduction: 5/magic and piercing
-Spell Resistance: 20
-Figurehead: This reinforced battering ram houses the main cannon and takes on the likeness of its current captain (or the last to use it).
-Damage Reduction: 50/magic and piercing
-Spell Resistance: 40
Movement (add 50' if figurehead is destroyed):
-Land: Flight 50' (poor), no attacks
-Battle: Flight 50' (poor), allows for three attacks that round.
-Cruise: Flight 100' (average), allows for one attack that round.
-Pursuit: Flight 200' (perfect), no attacks that round.
Hallowbane must hold its current speed setting for 1d3+1 rounds before advancing up or down in its movement modes.
It takes twenty minutes for Hallowbane to take off for the first time after being docked for 24 hours or more. After that, it takes five minutes for Hallowbane to take off or land.
Size: Colossal (100 feet long by 50 feet wide by 40 feet high)
Strength: 45 (For the purpose of bull-rushing and ramming.)
Fortitude Save: +20
Reflex Save: +20
Will Save: +20 (Mindless)
(See the Heart of the Captain ability)
Points of Interest:
This is the nerve-center of the mighty sky beast. Unlike its deeply inferior brethren, Hallowbane's bridge is located in the belly of the ship where it is nigh invulnerable. It is here that the captain takes charge over the actions of the ship and its crew. The captain is often a CR 18+ evil extraplanar outsider, with Leadership. A captain can take hold of the mutable nature of the ship's shadow-forged interior and create any assortment of rooms and corridor they like; the position of the Bridge, Gunnery, and Shadow Engine, as well as main corridors along the hull and main points of interest cannot be altered. This can be used to trap enemies within.
This is where the weapons of Hallowbane are coordinated. There are actually three gunnery stations: one for the Main Cannon, another for Spine-based attacks, and a third for any other attacks. Clearing out a gunnery station will render that weapon inoperable. It takes a DC 20 Know (the planes, or arcana, or engineering and architecture) check to use one of the weapons for oneself. And such a sabotage attempt has a 10% * (outcome - 20) to be the first attack in the 'queue' that round. Otherwise it does not fool the captain's control, who ultimately decides on whether or not an attack is made.
If a pure heart were to beat within the chest of Hallowbane, the unnatural cadence of the Shadow Engine would be it. This ancestral source of power was dredged up from the lowest point of the Plane of Shadow and fitted to serve as the core of Hallowbane. It powers all of the ships weapons and movement systems. If one could find their way into the engine room and destroy the Engine, it would destroy the ship once and for all.
The perfect black sphere measures five feet wide and is protected within a tainted prismatic sphere (50% of damage is vile damage, DC 30, CL 18). Any negated layer reforms after 1 minute per level of the destroying effect's caster level. Once all the layers are disabled, a saboteur has access to a concentrated piece of the Plane of Shadow. Any living creature in the engine room takes 1 negative energy level per round. A brilliant energy weapon or 7th level or above [Light] spell unleashed within the core is enough to do the job (or a magic item which is made with such a spell). The weapon is destroyed absolutely and the spell slot used to cast the spell is rendered unusable for 1 week.
Once destroyed, the ship decays at a rate of 50 damage per round to each remaining part. Crew members and the captain are paralyzed as the inevitable destruction ensues. The ship is now uncontrollable and will crash in one round per 50 feet above the ground (dealing 20d6 damage to anyone inside, and 10d6 to everything within fifty feet of the crash site). If the ship crashes or the hull is reduced to 0 hitpoints, a void opens up where the core should have been. All pieces of the ship, along with the remains of its crew and captain are pulled into this absolute darkness, one very much like the Shadow Engine. To what oblivion they are cast is unknown... Only the destruction Hallowbane has sown is left behind. Any undead created by the Aerie of Souls or the Main Cannon are destroyed (along with any undead they may have spawned).
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I like this; two issues; First, for the main cannon instead of transporting stuff to the plane of shadows (which seems to be overkill even for this object) I'd remove that entirely and add that if the target is not living then it is subject to a Disintrgrate spell with CL 18. This also has the advantage that this actually allows the main cannon to be used on things like fortresses.
Second, Aerie of Souls releases 2d10 bat swarms, 1d6+2 dire bats or 2d4 shadows. I'm not sure anyone would almost ever choose the first two options instead of the third given how much harder shadows are to deal with. Also, for all of these creatures and for all undead created by the various weapons, are they under control of the ship? I'd at least add a note that anything released by the Aeire of Souls will automatically treat the ship as an ally, not attack it, attack things that it is attacking or are attacking it. etc.
it is extremely well thought out, even up to being able to flip itself and fire a meteor at the ground. But, one question: The main cannon takes two rounds to charge, draining attacks each round, but what is the attack cost when firing on the third round?
How many attacks does the ship get /round? It just says a certain number. (up to the DM?)