Infernal Machine Rules

Crashing and Ramming

When an infernal war machine crashes into something that could reasonably damage it, such as an iron wall or another vehicle of its size or bigger, the infernal war machine typically looses speed and takes 1d10  bludgeoning damage for every 10 feet of relative speed (maximum 20d10).

• If the rammed vehicle is +2 size classes, larger the damage is halved.
• If the rammed vehicle is 2 size classes smaller, it is doubled
• The damage taken by the ramming vehicle is adjust up or down similarly based on relative size. 
  

Regardless of whether or not the infernal war machine takes damage, each creature on or inside the vehicle when it crashes must make a DC 15 Strength saving throw, taking the same damage if they fail, but none on the event of a successful save

The type of crash can effect these numbers.

Having worked out damage, and assuming the rammer is not immobilized by the impact, the rammed vehicle is pushed out of the path of the rammer. Usually it will be obvious which way the target vehicle should be pushed aside. If it is not obvious then push the target randomly to the left or right of the rammer’s path (D6 – 1, 2, 3 left; 4, 5, 6 right). The target is then swerved 45° in the direction it has been been pushed. Again, the direction the vehicle swerves in will usually be obvious, but if not a random dice roll will decide.

Once the target vehicle has been pushed aside the rammer must complete his full move in a straight line.

Avoiding a Ram

If you attempt to ram a moving enemy vehicle then the enemy driver can attempt to swerve out of the way at the last minute. Roll opposed dexterity checks.  

Note that an immobilized vehicle, or a vehicle which did not move in its previous turn and which is therefore judged to be stationary, cannot try to avoid a ram.

T-Boning

If an enemy is struck in the side by the front of the attacker that is it's size or larger, that is considered a T-Bone. The attacker only takes half ramming damage. 

Ramming Enemies on Foot

Rather then an opposed dex check, the target makes a dex saving throw with a difficulty of 10+speed of the attackers. On success, no effect, however on failure the target takes double damage and is knocked prone. 

An infernal war machine that is at least two size categories bigger than the creature it crashed into can continue moving through that creature’s space if the infernal war machine has any movement left. Otherwise, the vehicle comes to a sudden stop, and each creature on or inside the infernal war machine when it crashes must make a DC 15 Strength saving throw, taking 1d6 bludgeoning damage for every 5 feet the vehicle moved since its last turn (maximum 20d6), or half as much damage on a successful save.

Crashing into Obstacles

While speeding around amongst rocks, wreckage and other obstacles is great fun, it’s fairly inevitable that vehicles will end up crashing into them.

Demons often scatter crude metal ‘truk traps’ around their forts just to make life hard for their opponents. Usually a crash will be less serious than a proper ram, although running head first into a rock can be very serious indeed!

If a vehicle crashes front-first into an obstacle its move of size +1 to it's size or smaller, treat the attack as a ram.

If the vehicle crashes front first into an obstacle of size class 2+, its move ends immediately and it suffers double ram damage. 

Falling

When an infernal war machine goes over a cliff or otherwise falls, the vehicle and all creatures on or inside it take damage from the fall as normal (1d6 bludgeoning damage per 10 feet fallen, maximum 20d6) and land prone.

Feeding the engine

Infernal machines are powered by steam engines that consist of boilers heated by imprisoned mephits  These mephits require one vile of demon ichor per day or else they will begin to loose power and may even die. 

For each day the engine is not fed, the machine looses one point of speed. In addition any demonic ichor fed to the engine will only rectify the backlog of feeding until the engine is fully fed.

Demon Ichor Boost

Provided the engine is fully fed, pouring a flask of demon ichor into an infernal war machine’s boiler doubles the vehicles speed for one turn. This is equivalent to a "dash" action, doubling the speed of the vehicle.

However performing this repeatedly in a short time frame is dangerous. For each subsequent boost, roll a d10 to check for a mishap. The first roll generates a mishap on a roll of 1, the second on a 1-2, etc. If a mishap occurs roll on the boost mishaps table. 

Giving the engine a short rest removes this penalty.

Bikes, Trikes and Copters work a little differently from the heavier tracked war machines.

• These vehicles are generally extremely fast but cannot benefit from demonic ichor
• They do not use the turn ruler, but can turn freely in any direction
• They often have very high AC's due to this speed
• They have no armor or damage thresholds and only a single pool of hitpoints
• When they are destroyed, the driver is considered killed. 

Rocket Spear:

Rocket spears are man portable consumable weapons consisting of a 10' wooden pole with a gunpowder charge and a percussion cap at the tip. They inflict 3d10 damage on use, and are destroyed.

Harpoon Anchors:

This is a vehicle mounted weapon who's primary purpose is to tether and slow and enemy. A spring-loaded device fires a grappling hook attached to a chain. On successful hit the grapple attaches to the target vehicle. The anchor, which is attached to the other side of the chain, is then detached. The anchors are designed to slow the target, the smaller versions will subtract 1 from the max speed, the larger will subtract 2. 

Breaking the anchors is possible either with melee weapons or with a driving test DC 20. 

Starting the Chase:

Determine the starting distance based on a Perception (Wis) role

Determine relative velocities: Note "Dashing" can only be performed via application of demon ichor for Infernal War Machines . For characters on foot or flying it is limited to 3 + its Constitution modifier. Each additional Dash action it takes during the chase requires the creature to succeed on a DC 10 Constitution check at the end of its turn or gain one level of exhaustion.

A chase participant can make attacks and cast spells against other creatures within range. Apply the normal rules for cover, terrain, and so on to the attacks and spells.

Chase participants can’t normally make opportunity attacks against each other, since they are all assumed to be moving in the same direction at the same time. However, participants can still be the targets of opportunity attacks from creatures not participating in the chase. For example, adventurers who chase a thief past a gang of thugs in an alley might provoke opportunity attacks from the thugs.

Ending The Chase

The chase ends when one of the chasers is disabled or surrenders, or escapes. If neither side gives up, both sides make opposed Driving (Dex) tests. If there are multiple vehicles on each side, make one role for each type of vehicle (Bike, Buggy, Battlewagon) using the best driving score for each class.

Apply the relative velocity to the roll as a bonus for the faster creature.

In the event the faster vehicle is the winner, that vehicle gains distance equal to the relative velocity.

In the event the slower vehicle wins, the distance remains unchanged

If the distance ever becomes > 500 the pursued may begin to make opposes Stealth / Perc roles. If the roll is successful, the vehicle escapes and the chase ends

Complications 

Complications occur randomly. Roll a d20 at the end of its turn. Consult the appropriate table to determine whether a complication occurs. If it does, it affects the next chase participant in the initiative order, not the participant who rolled the die. The participant who rolled the die or the participant affected by the complication can spend inspiration to negate the complication.