Iomandra Campaign Ship Combat Rules

We've modified the rules posted on the Wizards of the Coast community to include grappling an boarding.

See Exploration Vessel: The Steadfast and Privateer: Destiny's Mistress for ship stats and shipboard weapons. Note that unless the PCs have either explicitly purchased a ship-to-ship weapon or built the Thundershot Ballista, the ship is effectively unarmed.

Ship-to-ship combat plays out on a standard 1-inch-square grid, but each square represents roughly 100 feet (20 squares at character scale). Each ship occupies a single square.

Initiative: At the start of ship-to-ship combat, each captain rolls initiative. A ship’s initiative modifier is the same as its captain’s (+0 if the ship has no captain).

Movement: A ship moves its speed before and after taking actions (described below). If the ship has less than minimal crew, it moves at half speed.

Crew: A ship with less than minimal crew moves at half speed and loses 3 actions per turn.

Bloodied: When a ship is first bloodied in an encounter, one of its weapons (determined randomly) is destroyed. While a ship is bloodied, the ship and all creatures aboard take a –2 penalty to attack rolls.

Actions: On its turn, between moves, a ship gets 5 actions (–2 actions if its captain is absent, helpless or dead, and –3 actions if the ship has less than a minimal crew). Actions include making a skill check to gain a tactical advantage, firing a shipboard weapon, and ramming. As a matter of protocol, the captain usually decides how many weapons to fire versus how many skill checks to make on a ship’s turn. Ramming is a special action, described below.

Standard turn:

• First Move
• 5 Actions:
  • Skills
  • Attacks
• Second Move

Skill checks must be resolved before making attacks with shipboard weapons. Making a skill check in ship-to-ship combat costs 1 action regardless of whether or not the check succeeds. No skill may be used more than once on a ship’s turn. The skill check is made by a crew member — either a player character or a nonplayer character. The aid another rule applies, as normal.

The following skills apply:

Acrobatics (DC high): Your evasive instincts kick in. Your ship gains a +2 bonus to AC and Reflex until the start of its next turn.

Arcana (DC high): You manipulate subtle arcane energies to fortify your ship. Your ship gains 10 temporary hit points as well as a +2 bonus to Fortitude until the start of its next turn.

Athletics or Nature (DC medium): You command the rigging or harness the winds to your advantage. Your ship can move 1 square before each shipboard weapon attack it makes this turn.

Bluff (DC high): You mislead the enemy. The enemy ship loses 1 action on its next turn.

Diplomacy or Intimidate (DC medium): You coordinate the attack on the enemy. Any attack made by your ship until the end of its next turn deals half damage on a miss.

Diplomacy or Intimidate (captain only; DC high): You motivate the crew in ways your enemy cannot. Until the end of this turn, whenever your ship makes an attack using a shipboard weapon, make two attack rolls and use the higher result.

History or Insight (DC medium): You are versed in naval battle tactics and can anticipate your enemy’s maneuvers. Your ship gains a +2 bonus to attack rolls until the end of its current turn.

Perception (DC high): You see a structural weakness or tactical flaw that can be exploited. Until the end of your current turn, the enemy ship gains vulnerable 10 to your ship’s attacks.

Religion (DC high): You call upon Melora, the Harridan, or some other great power to grant you favor in battle. Until the end of your current turn, your ship scores a critical hit on a natural roll of 18, 19 or 20.

Ramming: Ramming another ship costs 3 actions. The ramming ship, which must be at least 2 squares away from the enemy ship at the start of the ram, immediately moves a number of squares up to its speed into a space adjacent to the enemy ship. If it cannot reach an adjacent square, it cannot perform the ram action. The ramming ship then makes an attack (+0 vs. Reflex) against the enemy ship. Apply a –5 penalty to the attack if the ramming ship has less than a minimal crew. If the ram attack succeeds, both ships take the specified amount of damage, and neither ship can take actions on its next turn.

Grappling: Attempting to grapple costs 3 actions. After the first move, if the active ship is immediately adjacent to the target ship, roll an opposed check of the attackers choice from: Athletics, Acrobatics, or Bluff. Success equals a grapple and the ships are now immobile and may not attempt a move action without first breaking the grapple. The attacker's turn ends immediately - no additional action. At the start of his next turn, his crew may board the target.

Breaking The Grapple: On the one turn immediately after being grappled, there may be one attempt to break the grapple before being boarded. For a cost of 5 actions (may not be attempted with fewer): make one Hard DC Athletics roll by the captain at a -5 penalty (standard assist rules apply). Success means the grapple is broken, and the ship may immediately take it's movement to escape. This may be attempted only once per combat.

Boarding: If a captain grappled a ship in his last turn, he me either willfully break the grapple (for 3 action cost) or he may dispatch crew members across the lines/planks, etc. to board the target ship. This action replaces the current strategic scale map with a standard tactical combat map showing the decks of the two ships. Standard combat rules now apply - go to We're Boarded!

Firing a Shipboard Weapon: Attacks are resolved after skill checks, and firing a shipboard weapon costs 1 action. Unless noted otherwise, no shipboard weapon may be fired more than once on a ship’s turn, and ranged shipboard weapons can be fired without provoking opportunity attacks from adjacent ships.

Critical Hits with Shipboard Weapons: A critical hit deals maximum damage plus 1d10 extra damage per enhancement bonus of the weapon. As an option, the attacker can choose to treat the critical hit as a normal hit and also reduce the target vessel’s speed by 1. Whenever a ship takes a critical hit, roll 3d6: If you roll doubles or triples, the ship loses a number of crew equal to the highest die result. (For example, if you roll a 2, 2, and 5, the ship loses 5 crew.) A player character aboard the target ship can, as an immediate action, spend a healing surge to negate 1 crew casualty.

Shipboard weapons can be attacked independently of the ship they're on, and unlike ships they are not immune to melee and ranged attacks from creatures. A shipboard weapon typically has the following statistics: HP 80, AC 25, FORT 25, REF/WIL 0.

A standard shipboard weapon requires a crew of two to operate: one to load and aim the weapon (standard action) and one to fire and reset it (standard action). The range is given in 100-foot squares (as opposed to 5-foot squares).

There are more examples on the original post.

A ship has hit points and defenses like any vehicle. However, a ship can only be damaged by shipboard weapons as well as close and area attacks that damage objects. While a ship is bloodied, attacks made aboard the ship (including attacks made with its shipboard weapons) take a –2 penalty.

A damaged ship can be repaired at a cost of 100 gp per hit point, provided there's equipment and replacement parts available to complete the repairs. Each hit point of damage requires 1 man-hour to repair.