Siege Weapons

These Siege Weapons rules recreate the brutal reality of siege weapon impact from a creature point of view. As such, damages are balanced towards realism and do not consider player survivability a priority. An impact with a siege weapon is intended to cause instant death or severe injuries beyond those of adventuring life. You have been warned!

In a campaign where siege warfare is essential, the GM should introduce Siege Weapon proficiency. Players can receive it as part of their background instead of another tool proficiency, or spend downtime days and gold to learn it.

Medieval Direct Firing Mechanical Artillery
Name Cost DR/Integrity Aim Range Damage Crew Load Size Weight
Ballista, 1-lb. 1,960 gp 10/50 +10 750/900 4d10 1 2 Medium 1/2
Ballista, 2-lb. 2,450 gp 10/50 +9 750/950 5d10 1 3 Medium 1/2
Ballista, 5-lb. 2,940 gp 10/50 +9 800/1000 6d10 1 3 Medium 1
Ballista, 10-lb. 3,430 gp 10/50 +8 850/1100 7d10 1 4 Large 1
Ballista, 15-lb. 3,920 gp 15/50 +8 900/1100 8d10 1 6 Large 1
Ballista, 20-lb. 4,410 gp 15/50 +8 900/1200 9d10 1 7 Large 1
Ballista, 30-lb. 4,900 gp 15/50 +7 950/1250 10d10 2 18 Large 2
Ballista, 60-lb. 5,880 gp 20/50 +7 950/1300 12d10 3 27 Huge 4
Ballista, 180-lb. 7,840 gp 20/50 +6 1000/1300 16d10 6 66 Huge 12
Carroballista, .5-lb. 1,470 gp 10/50 +10 650/800 3d8 1 1 Large 1/2
Gastraphetes, 1-lb. 1,470 gp 10/50 +10 950/1200 3d8 1 3 Compact —
Gastraphetes, 4-lb. 2,450 gp 10/50 +7 900/1100 5d8 1 6 Medium 1/5
Scorpion, 27”, .5-lb. 1,470 gp 10/50 +10 650/850 3d8 1 1 Medium 1/3
Scorpion, 36”, 1.2-lb. 1,960 gp 15/50 +9 700/900 4d8 1 2 Large 1/2
Scorpion, 45”, 2.25-lb. 2,450 gp 15/50 +8 750/950 5d8 1 3 Large 1
Scorpion, 54” 4-lb. 2,940 gp 20/50 +7 750/950 6d8 1 4 Huge 1
Scorpion, 72” 10-lb. 3,430 gp 20/50 +6 800/1050 7d8 1 5 Huge 1
Arbalest, 0.5-lb. 1,470 gp 10/50 +2 1100/1400 3d8 1 4 Medium 1/3
Springald 2-lb. 2,450 gp 10/50 +5 250/350 5d8 1 3 Medium 1
Medieval Indirect Firing Mechanical Artillery
Name Cost DR/Integrity Aim Range Damage Crew Load Size Weight
Petrobolos, 5-lb. 2,900 gp 10/75 +9 750/950 5d10 1 6 Large 1/2
Petrobolos, 40-lb. 6,380 gp 15/75 +7 1000/1250 11d10 2 18 Huge 3
Monankon, 15-lb. 6,960 gp 15/75 +4 400/1300/1650 12d10 2 18 Huge 2
Mangonel, 2-lb. 4,060 gp 10/75 +5 45/150/200 7d10 15 30 Large 1/5
Mangonel, 5-lb. 4,640 gp 10/75 +4 50/150/200 8d10 30 60 Large 1/3
Mangonel, 10-lb. 5,800 gp 15/75 +4 50/150/200 10d10 50 100 Huge 1
Mangonel, 30-lb. 7,540 gp 20/75 +3 55/150/200 13d10 100 200 Huge 2
Mangonel, Weighted, 5-lb. 4,640 gp 10/75 +5 100/300/400 8d10 30 270 Large 1
Mangonel, Weighted, 10-lb. 5,800 gp 15/75 +5 100/300/400 10d10 50 450 Huge 1
Trebuchet, Small, 25-lb. 7,540 gp 15/75 +3 250/800/1000 13d10 25 1225 Huge 10
Trebuchet, Large, 80-lb. 10,440 gp 15/150 +2 270/850/1100 18d10 30 2220 Gargantuan 25
Trebuchet, Hinged, 25-lb. 6,960 gp 20/75 +3 450/1450/1800 12d10 25 1225 Huge 8
Trebuchet, Hinged, 80-lb. 9,860 gp 20/150 +3 500/1500/2000 17d10 30 2220 Gargantuan 22
Medieval Gunpowder Artillery
Name Cost DR/Integrity Aim Range Damage Crew Load Size Weight
Rocket, 1.2-lb. 100 gp —/25 +4 0/2500 2d12 1 2 Compact —
Bombard, 50-lb. 5,850 gp 15/75 +1 250/1650 13d12 4 36 Large 1
Bombard, 430-lb. 16,200 gp 20/75 +1 400/2200 36d12 4 36 Huge 8
Crapaudeau .12-lb. 450 gp 15/50 +4 50/500 1d12 4 36 Large 1/5
Veuglaire 2.5-lb. 1,800 gp 15/50 +4 150/1050 4d12 4 36 Large 1/3
Renaissance Gunpowder Artillery
Name Cost DR/Integrity Aim Range Damage Crew Load Size Weight
Rabinet, 0.6-lb. 2,000 gp 15/50 +6 270/2550 5d12 1 9 Large 1/5
Falconet, 1.5-lb. 2,800 gp 15/150 +5 350/3000 7d12 1 9 Large 1/4
Falcon, 3-lb. 4,000 gp 15/75 +5 400/3900 10d12 1 9 Large 1/3
Saker, 10-lb. 6,000 gp 15/75 +5 650/5700 15d12 3 27 Large 1
Culverin, 30-lb. 9,600 gp 15/75 +4 900/6500 24d12 6 66 Large 2
Cannon, 80-lb. 12,000 gp 15/75 +5 1050/7800 30d12 12 192 Huge 3
Field Cannon, support, 3-lb. 5,600 gp 15/100 +6 600/5400 14d12 1 9 Large 1/2
Field Cannon, large, 12-lb. 9,600 gp 15/100 +5 900/7200 24d12 5 45 Huge 2
Field Cannon, fort, 24-lb. 12,000 gp 20/150 +4 1100/8100 30d12 7 77 Huge 4
Ship’s Gun, 4-lb. 7,200 gp 15/100 +6 810/6900 18d12 2 18 Large 1/2
Ship’s Gun, 9-lb. 9,600 gp 15/100 +5 900/7200 24d12 4 36 Huge 2
Ship’s Gun, 18-lb. 11,200 gp 20/150 +4 1000/7800 28d12 6 66 Huge 3
Ship’s Gun, 42-lb. 14,400 gp 20/150 +3 1100/8400 36d12 11 154 Huge 4
Swivel Gun, 2.5-lb. 2,400 gp 15/50 +3 250/2700 6d12 1 3 Large 1/5
Crouching Tiger Gun, 1.2-lb. 2,400 gp 15/150 +2 200/1650 6d12 4 36 Large 1/5
Long-Range Awe-Gun 3-lb. 2,800 gp 20/200 +2 400/3600 7d12 4 36 Large 1/2
Siege Weapon Ammunition
Ammo Type Cost Weapon Type & Effect
Bolt 6 sp/lb. Impaling
Boulder 2 sp/lb. Crushing
Stone Cannonball 2 gp/lb. Explosive, Medieval
Iron Cannonball 8 sp/lb. Explosive, Renaissance
Burning +50 gp Target or area starts burning 1d6/round for rounds equal to weapon dice of attack.
Shrapnel +100 gp +3 to hit the Dexterity defence of creatures in AoE. A miss still deals half damage.

Siege Weapon Damage Types

Siege Weapons introduce three new types of damage: impaling, crushing and explosive.

Impaling

Impaling damage is dealt by direct fire artillery such as the ballista. Their projectiles need to hit the target exactly to deal damage so they are best against immobile structures.

Crushing

Crushing damage is dealt by indirect fire artillery such as the trebuchet. Their projectiles are large and bulky and threaten a small radius around the impact point. They can do damage to immobile structures even if they near miss, but creatures can attempt to evade to avoid any damage.

Explosive

Explosive damage is dealt by gunpowder artillery such as the cannons. Their projectiles are shot at high velocity and they shatter and threaten a radius around the impact point. They can do damage to immobile structures even if they near miss, and creatures can attempt to evade to only take half damage.

Structures and Materials

Structures made of solid material have Damage Reduction based on the material they are made from. Subtract DR from any damage dealt to them unless they are vulnerable to the damage type. Their size determines the base siege defence and the smaller the target is, the harder it is to hit.

Material Vulnerable To… DR Integrity/Foot
Wood Explosive, Impaling 5 120
Stone Explosive, Crushing 8 180
Iron/Steel — 10 240

Siege Weapon Properties

Ammunition Weight

The ammunition caliber and weight (pounds per unit) are listed at the end of the siege weapon’s name.

DR and Integrity

To make a melee or ranged attack against an immobile siege weapon you must make an attack roll of 10 or better. If you hit, subtract the siege weapon’s DR from the damage and subtract the remaining damage from the siege weapon’s integrity.

Aim

To fire a loaded siege weapon, you must make an Intelligence (Siege Weapons proficiency) skill check. Add the Aim bonus or penalty of the weapon to your roll.

Range

Some siege weapons have three range values. The first value is the minimum range it can shoot at. The second and the third value are the Near and Long range.

Crew and Load

To load a siege weapon with a single unit of ammunition one or several creatures must commit a number of actions to clean and prepare the weapon to fire. Once actions equal to the load value are spent, the weapon is ready to fire.

Only a limited number of creatures can work on a siege weapon together, up to the Crew value.

Size and Weight

Size category defines how massive the weapon is. Compact weapons can be lifted with two hands and shot like ranged weapons. Huge or Gargantuan weapons require special platforms to be moved around, or need to be assembled by skilled personnel. When mounting such weapons inside a vehicle (such as a ship) the vehicle will have a limited number of weapon slots of specific size.

The Weight is represented by a number of horses required to pull a cart containing the weapon and roughly equals a US tonne (2000 pounds). Values of 1/2 or 1/3 means multiple weapon can be transported with a single cart, and is limited to weapons Large or smaller. When the value is 2 or more, a wagon capable of being pulled by several animals is needed, or the weapon must be disassembled and parts of it carried by several carts. Huge creatures (i.e. elephants) count as two horses but require special carts or platforms.

Siege Weapon Actions

Push/Move Weapon

When a siege weapon is built, assembled or placed stationary it is considered to be facing in a chosen direction (including diagonals). The weapon can only fire in that direction. Only if mounted on a mobile platform, vehicle or a living creature, its direction may change on command.

You can spend your action during combat to push or pull a siege weapon to change its direction of fire, or move it to a new position. To do this with a Large siege weapon you must have Strength score 13 or more and make a DC 15 Strength (Athletics) check.

For each size category above Large, raise minimum Strength score by +2 and DC by 5. The GM may allow you to roll with advantage if the weapon has means to rotate or move (such as wheels) or impose a disadvantage if has large friction area and stationary.

Size Strength DC
Medium — 15
Large 13 20
Huge 16 25
Gargantuan 19 30

A number of creatures that meet the Strength requirement can Help you, up to the Crew value of the siege weapon.

If you attempt to move to siege weapon and succeed, it can be moved up to half your speed if Large or smaller, or only by 5 feet if Huge. Gargantuan siege weapons cannot be moved without wheels, platforms or beasts of burden.

Once a siege weapon is moved or repositioned, it is no longer Aimed and all Aiming benefits are lost.

Aim

Aiming involves precise targetting or trajectory calculation that improve the odds of hitting the target. To Aim a siege weapon during combat, spend your action to make a DC 15 Intelligence (Siege Weapon proficiency) check. Only one creature can Aim with the same siege weapon, up to a number of times equal to its Intelligence modifier. On success, an effect is applied to the next Fire action:

Precise Targetting. You gain advantage to the next Fire action with the siege weapon. This advantage ignores the general rule for only one advantage to the roll. You can take this option multiple times, each time adding one more d20 die to your next Fire action.

Predict Positioning. When you fire a siege weapon that deals impaling or explosive damage against a target that moved during its previous turn (such as creature or a vehicle), you ignore defence bonuses from movement. Effect is ignored if the target chooses not to use its movement during any of its following turns prior the Fire action.

Calculate Trajectory. When you fire a siege weapon that deals crushing damage, it will ignore half and three quarters cover unless the cover is positioned above the target.

Collateral Damage. When you fire a siege weapon that deals explosive damage, instead of doing collateral damage on missing the defence by 2 or less, you do so on missing the defence by 4 or less.

Fire

Fire is either manual action or a given command to an ally who fires the siege weapon. Firing a siege weapon is not a ranged attack, and abilities and feats that benefit ranged attacks do not apply. After the weapon is fired, all Aiming benefits are lost.

You can either spend your action to fire a siege weapon. Make a Dexterity or Intelligence (Siege Weapon proficiency) check and add the weapon’s Aim modifier. You must meet or beat the siege defence of the target.

The Aim action allows you to roll one or several extra d20 and take the highest result. You always hit if you roll more natural 20s than natural 1s with all dice.

The siege defence of the target is based on its size, movement, or evasion ability. Use the tables to calculate the defence by choosing a base and applying related modifiers.

Target Size Base Defence
Size Example Base Defence
Medium Humanoid, pile of munition 25
Large Siege weapon, small tent 20
Huge Single floor building 15
Gargantuan Two or three floor building 10
Colossal Temple, a large tower 7
Titanic Large castle 5
Target Mobility Modifier
Speed Example Near Range Long Range
Stationary Any building — —
Slow
20 ft. or less		 Moving siege weapon +5 +10
Steady
30 ft. to 50 ft.		 Squad of footmen +10 +15
Fast 55ft. or more Charging horsemen +15 +20
Target Armour Modifier
Speed Modifier
For each 3 points of natural armour +1
For each 2 point Dexterity bonus to armour +1
Cover Modifiers

For a structure or creature to benefit from cover, the cover should not be smaller than one size category below the size of the target.

Cover Visibility Modifier
Half Cover Night, fires illumination +2
Three Quarters Cover Night, clear moon +5
Almost Total Cover Night, cloudy +10

Damage Resolution

Impaling

Siege weapons that deal impaling damage do so only if your Fire check is equal or greater than the siege defence of the target.

Crushing

Siege weapons that deal crushing damage cause damage to all targets in radius of their impact point. The size of the affected area is based on the number of damage dice.

Size of Impact Area

Damage Dice Radius, ft
3–4 5ft.
5–7 10ft.
8–11 20ft.
12–16 30ft.
17–30 60ft.
31+ 120ft.

Make an attack roll vs the Dexterity defence of all targets in the affected area. The attack bonus is based on the die size of the siege weapon (see table below). If the attack misses, the creature takes no damage.

Die Size Attack Bonus
d8 +1
d10 +3
d12 +5
d20 +7

Explosive

Siege weapons that deal explosive damage cause damage to all targets in radius of their impact point. The size of the affected area and attack bonus are the same as those of siege weapons that deal crushing damage. However, creatures that are missed take half damage instead of no damage.

Siege weapons that deal explosive damage also cause a lot of collateral damage. Even if the siege weapon misses the Dexterity defence by 2 or less, it still hits. However, structures take half damage and creatures that are missed take no damage.

Siege Damage Injuries

For living creatures, a siege weapon impact is almost a death warrant. Not only you may die, but the prospects of finding remains of your body or being able to resurrected it may be uncertain.

If siege damage deals more than half your max stamina and reduces you to 0 stamina, you suffer a siege injury. Roll on the Siege Injury table. Roll with advantage if the damage is impaling. Roll with disadvantage if the damage is explosive.

Strongholds & Followers

These weapons are compatible with Strongholds & Followers by MCDM Productions. To convert to S&F, the Power Bonus is equal to the number of dice of the weapon damage.