Siege Weapons

Siege engines assault structures and people from a distance by propelling ammunition in some fashion.

The following rules are a modified version of the siege engine rules found in Pathfinder RPG Ultimate Combat, and focus only on those siege engines that can be carried and used on board ships.

Siege Engine Basics

All siege engines in the Skull & Shackles Adventure Path use the following basic rules, unless stated otherwise in an individual siege engine description.

Proficiency: Siege engines are exotic weapons. The Exotic Weapon Proficiency feat allows a character to fire a single type of siege engine without penalty. A creature with the Siege Engineer feat (Ultimate Combat 118) is proficient with all siege engines.

Feats: Several feats presented in Ultimate Combat can be used with siege engines. These include the following: Master Siege Engineer, Siege Commander, Siege Engineer, and Siege Gunner.

Crew: The sheer size of a siege engine often necessitates a crew for its use. One person of that crew is the crew leader. Usually the crew leader controls the movement of a siege engine or designates its targets; sometimes the crew leader does both. Often the crew leader is required to take actions and make specific checks in order for a siege engine to function. The rest of the crew members are required to spend actions and make checks in order for a siege engine to function. The crew of a siege engine is in addition to the crew needed to operate the ship.

Constructing Siege Engines: A siege engine is a complex device requiring a DC 20 Craft (siege engine) skill check to build.

Magical and Masterwork Siege Engines: Siege engines can be masterwork, increasing their Craft DC by 5 and cost by 300 gp. A masterwork siege engine can be enchanted at twice the cost for a normal magical weapon. The enhancement bonus of a siege engine applies on attack rolls and targeting checks (in the case of indirectfire siege engines).

Disabling Siege Engines: A siege engine is considered a difficult device to disable, requiring 2d4 rounds of effort and a DC 20 Disable Device check to do so. When a siege engine is disabled, it either doesn’t work or is sabotaged and stops working after 1d4 minutes of use.

Repairing Siege Engines: Repairing a broken or disabled siege engine requires a DC 20 Craft (siege engine), Disable Device, or Knowledge (engineering)
check. It takes 10 minutes to fix the device, and the check can be retried if the fix fails.

Defense and Hit Points: All siege engines are objects, typically crafted out of wood. A siege engine has a Dexterity of 0 (–5 penalty) and a further penalty based on its size. Each type of siege engine has its own hardness and hit points. Siege engines can be armored—treat the siege engine as a creature of its size to determine the cost of the armor. Masterwork siege engine armor can be enchanted for twice the normal cost to enchant armor.

Armored siege engines gain an armor bonus to AC equal to that normally granted by the specific armor (shields have no effect on a siege engine), a hardness and hit points equal to that of the armor, and bonus hit points equal to the armor bonus ×5.

Assembling Siege Engines: Siege engines can be broken down for storage or transport and can be reassembled on a ship’s deck. A Large siege engine requires 1 hour and four workers to assemble. A Huge siege engine requires 2 hours and six workers to assemble. Each assembly worker must make a DC 10 Craft (siege engine) check; if untrained, the worker may not take 10. Assembly can be performed with at least half the required number of workers by doubling the time required. If fewer than half are available, the siege engine cannot be assembled.

Firing Siege Weapons

Siege engines hurl massive projectiles in one of two ways: direct fire or indirect fire. Both take a number of actions to load or aim, and the basic rules are described below.

Load Ammunition: In order for a siege engine to fire, it must be loaded with ammunition. Loading ammunition takes a number of full-round actions depending on the siege engine (this time can be reduced to move actions if the crew leader has the Master Siege Engineer feat [Ultimate Combat 109]).

For example, a light ballista loaded by two creatures takes 1 round to load the siege weapon, since the creatures each take one of the two necessary full-round actions to do so.

Aiming a Siege Engine: Siege engines must be aimed in order to attack a desired target (in the case of direct-fire siege engines) or square (in the case of indirect-fire siege engines). Aiming takes a number of full-round actions depending on the siege engine. Aiming a siege engine with a diminished crew doubles the amount of time it takes to aim the siege engine. Each time a new target or square is chosen as the target of a siege engine’s attack, that siege engine must be aimed anew. For example, a light catapult aimed by two creatures would have to spend a turn aiming the catapult in order to fire it on the next round, since a light catapult takes two full-round actions to aim. If the same light catapult were instead crewed by three creatures, two could spend full-round actions aiming it and the remaining creature could fire it with a standard action.

Direct-Fire Siege Engines: Direct-fire weapons launch their projectiles on a relatively flat trajectory, allowing them to more easily target creatures or pummel barriers directly in front of them.

A direct-fire weapon uses a normal ranged attack roll, with the normal penalty for nonproficient use if none of the crew operating it have proficiency in siege engines. In addition, a direct-fire weapon takes a penalty on attack rolls of –2 per size category that the weapon is larger than the creature aiming it. Creatures with ranks in Knowledge (engineering) are not adversely affected by their size when firing direct-fire siege engines. Sheer manpower can also reduce the penalties for size. Increasing the crew of these weapons by 1 or more can reduce the attack roll penalty for creature size: as long as an extra crew member is no more than three size categories smaller than the direct-fire weapon, it can reduce the penalty due to the aiming creature’s size by 2.

For example, a Huge ballista fired by a Medium creature that is part of a crew of four (one more than the minimum number of crew members required) takes only a –2 penalty on attack rolls, and a crew of five would negate the penalty altogether.

Indirect-Fire Siege Engines: Indirect-fire weapons launch projectiles in high arcs toward their targets. They typically lob heavier missiles and payloads than direct-fire weapons, but they are harder to aim accurately. Indirectfire weapons can bypass many forms of fortification, delivering their payloads of solid shot, scatter shot, or even disease-ridden offal to targets on other ships.

Indirect-fire weapons use a targeting mechanic similar to that described for catapults in the Core Rulebook, hereafter referred to as an indirect attack.

The following is an update to those rules.

Indirect Attack: To fire an indirect-fire siege engine, the crew leader makes a targeting check against the DC of the siege engine. This check uses his base attack bonus, his Knowledge (engineering) skill modifier if trained in that skill (or his Intelligence modifier, if not trained), any nonproficiency penalty, and the appropriate modifiers from Table 2. If the check succeeds, the ammunition of the indirect attack hits the square the siege engine was aimed at, dealing the indicated damage or effect to any object or creature within the area of its attack. Creatures may get a saving throw to limit the effect of the attack; this is typically based on the type of ammunition used.

If the attack misses the intended square, roll 1d8 to determine in what direction the shot veers. A roll of 1 indicates the ammunition falls short (toward the siege engine), with rolls of 2 through 8 counting squares clockwise around the target square. Roll 1d4 for every range increment at which the attack was made (1d4 if the target square is within the engine’s first range increment, 2d4 if the target square is within the second range increment, and so on). The total is the number of squares by which the attack misses. The ammunition deals its damage and any other effects in the square it lands on.


Critical Hits: When a direct-fire siege engine scores a critical hit, it confirms the critical and deals critical hit damage just like any other weapon. If an indirect-fire siege engine rolls a natural 20 on its targeting check, it can also score a critical hit. The crew leader must reroll the targeting check to confirm the critical. If the confirmation targeting check is successful, the attack is a critical hit, and the siege engine multiplies its damage by its critical multiplier. Unlike normal attacks, siege engine attacks can deal critical hit damage to objects. Siege engines do not gain the benefit of critical feats the crew or the crew leader may have.

Mishaps and Misfires: Rolling a natural 1 on an attack roll with a direct-fire siege engine or a targeting check made by an indirect-fire siege engine produces a mishap. Usually a mishap applies the broken condition. A siege engine with the broken condition takes a –2 penalty on attack rolls, targeting checks, and damage rolls. If the creature that serves as crew leader has the Siege Engineer feat, that creature does not generate a mishap on a natural 1 when firing the siege engine.

Siege Weapon Descriptions

The following siege engines are available in the Skull & Shackles Adventure Path.


A ballista resembles a massive crossbow, and its power is provided by twisted skeins of animal sinew used as torsion springs driving a pair of adjustable arms. A cord attached to both arms is winched back and a projectile is loaded into a grooved slider for release. Ballistae are direct-fire siege engines.

Light: This common type of ballista, also called an arbalest or scorpion, is Large, maneuverable, and often mounted on ships. Light ballistae have a hardness of 5 and 50 hit points. Light ballista bolts cost 10 gp each and weigh 10 pounds.

Heavy: These Huge siege engines are commonly used as castle defenses, as well as on large warships. Heavy ballistae have a hardness of 5 and 100 hit points. Heavy ballista bolts cost 30 gp and weigh 20 pounds each.


Catapults are stone-throwing siege engines powered by winched arms that run through torsion skeins, and hold their payload in a cup that swings up and over the weapon when released. Catapults can hurl a variety of different types of ammunition (the damage given is for stone projectiles; other types of ammunition can be found in the Special Siege Engine Ammunition section, below). Catapults are indirect-fire siege engines.

Light: These catapults are Large and often mounted on wheels. The targeting DC of a light catapult is 15. Light catapults have a hardness of 5 and 50 hit points. Light catapult stones cost 10 gp and weigh 50 pounds each.

Standard: These Huge catapults are too large to be transported in one piece, and require assembly. The targeting DC of a standard catapult is 20. Standard catapults have a hardness of 5 and 100 hit points. Standard catapult stones cost 15 gp and weigh 75 pounds each.


A corvus is a boarding device that features a hinged counterweight system for mounting a bridge vertically on the side of a ship, with a hooked end to grab onto a target ship. A corvus is usually 10 feet wide and 15 feet long. It has a hardness of 5 and 10 hit points per square. Using a corvus requires a DC 10 Profession (siege engineer) check as a full-round action, provided the corvus is in the correct position, which is within the length of the corvus and adjacent to another ship. If the check fails, the corvus fails to catch on the target and must be reset (a full-round action). Once a corvus is attached, it takes a Strength check as a full-round action to dislodge the corvus. Alternatively, if the corvus is attached to a ship, the pilot of either ship can make a sailing check as a standard action to dislodge the corvus (a check that succeeds by 5 or more destroys the corvus). The base DC for either of these checks is 15, and the DC increases by 5 for every Small or Medium creature currently standing on the corvus. If a corvus is disengaged while creatures are standing on it, those creatures must make a DC 15 Reflex saving throw or fall. Succeeding at the saving throw allows them to move to the nearest area of safe ground, but such movement provokes attacks of opportunity.

A corvus cannot be armored. A corvus does not count toward a ship’s maximum number of siege engines.


These Huge siege engines are often mounted on wheels. This apparatus fires gouts of alchemist’s fire in either a 60-foot line or a 30-foot cone (siege crew leader’s choice). Targets in the area take 6d6 points of fire damage (DC 15 Reflex save for half damage); those who fail their saves also catch on fire. A firedrake with the broken condition that suffers a further mishap explodes, dealing its damage to all creatures within a 20-foot-radius burst (DC 15 Reflex save for half damage). Firedrakes have a hardness of 10 and 70 hit points. One use of firedrake ammunition costs 200 gp and weighs 20 pounds.


A springal uses a torsion-cranked composite paddle to strike a firing rack containing multiple arrows, which rain down in an arc over a burst area. Springals are indirect-fire siege engines that affect the targeted square and a 15-foot burst around that square. One use of arrow springal ammunition costs 20 gp and weighs 10 pounds.

Special Siege Weapon Ammunition

The following kinds of ammunition can be used in select types of indirect-fire siege engines. The ammunition description specifies which types of siege engines can use the special ammunition. The costs and weights on Table 4 are for individual uses of special ammunition.

Alchemist’s Fire: This is either a hard, ceramic container of alchemist’s fire that can be used as ammunition in catapults, or a ceramic bulb of alchemist’s fire mounted on the tip of a ballista bolt to be fired from ballistae. When it hits its target square, it deals 4d6 points of fire damage to each creature and wooden structure within 5 feet of the target space, and each creature must make a DC 20 Reflex saving throw or catch on fire (wooden objects automatically catch on fire). Every creature and wooden object within the area between 5 and 30 feet of the target space must make a DC 20 Reflex saving throw or take half the fire damage, but does not catch on fire. On a siege engine mishap, this ammunition explodes before it is launched, dealing its damage to the siege engine and all nearby creatures and wooden objects as if one of the spaces of the siege engine (crew leader’s choice) were the target square. This alchemical fire ignores the hardness of wooden objects.

Chain Shot: Made of two small catapult stones chained together, this ammunition can be fired from catapults. Chain shot is especially good at tearing through sails and rigging, dealing double its normal damage to that form of propulsion. It deals normal damage to a creature, and if hit, the creature must succeed at a DC 20 Fortitude saving throw or be knocked prone. Chain shot is relatively ineffective against ships themselves, dealing only 2d6 points of damage for a light catapult, or 4d6 points of damage for a standard catapult.

Liquid Ice: This hard, ceramic canister filled with alchemical liquid ice can be used as ammunition in catapults. When it hits its target square, it deals 4d6 points of cold damage to each creature within 5 feet of the target space, and each creature must make a DC 20 Fortitude save or become entangled for 1 round. Every creature within the area between 5 and 30 feet of the target space must make a DC 20 Fortitude saving throw or take half damage. On a siege engine mishap, this ammunition explodes before it is launched, dealing its damage to all nearby creatures as if one of the spaces of the siege engine (crew leader’s choice) were the target square.

Plague Bundle: This hard, ceramic canister is filled with a noxious mass of diseased carrion and offal that can be used as ammunition for a catapult. It deals only half damage, but every creature hit by it is exposed to filth fever (Core Rulebook 557). A GM might allow a plague bundle to inflict other diseases.

Smoke Shot: This hard ceramic sphere contains two alchemical substances separated by a thin barrier, much like a smoke pellet (Advanced Player’s Guide 185) in larger form. It can be used as ammunition in catapults. When smoke shot hits the target space, it deals 2d6 points of damage to any creature in that space, and the substances mingle and then create an area of foul but harmless yellow smoke radiating 30 feet from the target square. Treat the effect as a fog cloud spell. On a siege engine mishap, the ammunition explodes before it is launched. Its effect is centered on one of the spaces of the siege engine (crew leader’s choice).

Siege Weapons

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