Making the Rust Monster - WIP

The Rust Monster

Over the next few days I will type up my work converting the D&D rust monster. I will start by looking at the 5E stat block, found here - 5E SRD - Rust Monster

I will again rely heavily on my conversion formulas found here as a spreadsheet - 5E to Fbl conversion guide.

STEP 1: STRENGTH - As always the first question: Is it a monster? Well, it has MONSTER! as part of its name so definitely a monster. This means we use the Rust Monsters HD to determine its Fbl Strength. Because of this we also need to look for any immunities or resistances as this will affect the conversion multiplier. No immunities so 5D8 +5 converts to 5 * 1 (as a D8 hit has a conversion multiplier of 1) + 1 (the creatures Constitution Modifier) Giving a total of 6, which is quite low for a monster but this critter has additional protection with its rust ability, so it should be fine.

STEP 2: AGILITY - Agility is pretty straight forward, take the creatures Dexterity score and plug into my conversion table. 12 converts to 4.

STEP 3: WITS AND EMPATHY - Its a monster, and its 5E Int, Wis and Cha are too low to worry about, so lets skip this.

STEP 4: SKILLS - No skills listed, so we can move on.

STEP 5: MOVEMENT - 60ft / 30 = 2, its quicker than an average human, as it should be.

STEP 6: ARMOR RATING - The Rust Monsters AC is 14, subtract 10 gives us 4. This is the point where 5E head scratching comes in, as the armor rating could be modified by the creatures Dex modifier of +1, or it might not be, depending on how the AC is calculated. As we want the Rust monster to be a bit of a threat, lets just keep the full 4.

STEP 7: TYPICAL GEAR - Rust Monsters don't generally carry items, so we can skip ahead.

STEP 8: IMMUNITIES, RESISTANCE AND VULNERABILITIES - Nothing listed for any of these, which means it will take damage from all attacks but anyone using metal weapons is in for a surprise (unless they are old school D&D players, then they should not be surprised at all).

STEP 9: SPECIAL ABILITIES - The Rust Monster has two special abilities -

• Iron Scent: The rust monster can pinpoint, by scent, the location of ferrous metal within 30 feet of it. 

This is pretty easy to translate, just change 30ft to SHORT range, this is a bit longer as its up to 25m but that should be fine. I might add a description about how it would choose a target amongst a group of adventurers.

• Rust Metal: Any nonmagical weapon made of metal that hits the rust monster corrodes. After dealing damage, the weapon takes a permanent and cumulative -1 penalty to damage rolls. If its penalty drops to -5, the weapon is destroyed. Nonmagical ammunition made of metal that hits the rust monster is destroyed after dealing damage. 

This one is a bit trickier due to how weapons work in Fbl. My instinct is to make this immediately reduce Gear Dice but there is a little bit of me (probably my left eye) that wants me to only reduce Gear Dice if a 1 is rolled when attacking. For now I will go with my initial thought. I will add that the weapon also cannot be repaired to recover this lost Gear Dice.

STEP 10: CONVERT ATTACKS - The Rust Monster has two actions listed that can be converted to attacks. I will work through this tomorrow.

• Bite: Melee Weapon Attack: +3 to hit, reach 5 ft., one target. Hit: 5 (1d8 + 1) piercing damage. 

This one is easy to convert. The range is ARM’S LENGTH because of its 5ft reach. Cross reference the creatures Strength attribute of 13 with the conversion table to find the Base Dice increase, in this case it’s 3, and add this to the +3 to hit. The creature rolls six Base Dice to bite, and as it’s damage average is less than 20 it does Weapon Damage 1 in Fbl. Although it states piercing damage, in Fbl bites are usually slash wounds. The reason for this I think is that a bite has the ability to severe limbs, but a stab would only pierce a specific hit location.

• Antennae: The rust monster corrodes a nonmagical ferrous metal object it can see within 5 feet of it. If the object isn’t being worn or carried, the touch destroys a 1-foot cube of it. If the object is being worn or carried by a creature, the creature can make a DC 11 Dexterity saving throw to avoid the rust monster’s touch. If the object touched is either metal armor or a metal shield being worn or carried, its takes a permanent and cumulative -1 penalty to the AC it offers. Armor reduced to an AC of 10 or a shield that drops to a +0 bonus is destroyed. If the object touched is a held metal weapon, it rusts as described in the Rust Metal trait

This one is slightly more complicated as it’s not written up as an attack in the 5E version. Usually for something like Poison or Disease I make the strength of it it equal to saving throw DC -10, and I think this fits to show how accurate the attack is. But rolling one dice for an attack is pretty pointless in Fbl, so I will add in the creatures adjusted Strength as well (as above). This gives a total of four Base Dice for the attack. The damage is something special that I need to think about, it probably causes 1 point of Gear Dice damage per success for whatever object it attacks, armor or weapon. I would also think this attack can be parried but that just specifically damages the weapon.

STEP 11: ATTACK DESCRIPTIONS - This is where your imagination comes in, try to make the attacks sound interesting. For the bite I think it would have mandibles, due to being insectoid. The antennae attack is going to be a frenetic rubbing type of attack.

STEP 12: NEW ATTACKS - The first thing to decide here is how many attacks should it have? Animals or small creatures can have just a couple of attacks that are described in the main stat block, large creatures always have six but my rule of thumb is that monsters with less than 8 Strength have three attacks, modelling the Stone Raven from the Bitter Reach. This is just a general guideline and depends on how creative I can be with the attacks, if I can come up with six I will use six. For the Rust Monster I had two immediate ideas.

• The Rust Monsters tail is said to also corrode but I think that does it by hitting the target, I would say it is somewhere between the bite and Antennae attacks in regards to base dice, so let’s put it at five Base Dice and Weapon Damage 1 (blunt force) due to the way it can club its target. It also looks quite long, so let’s increase the range to NEAR. It will also corrode like the antennae.

• I did think the Rust Monster would barrel through anyone not carrying metal to get to a target it could feed off, with the ability to knock the target prone as well whilst knocking them aside. Let’s call this RUSH ATTACK! until I can come up with something better, it has the same attack chance and damage as the bite but as (blunt force), the target also needs to make a MOVE roll or end up prone.

• Maybe a disarm attack versus anyone brandishing a metallic weapon, same base dice as the tail but it grabs the weapon and the victim must make a MIGHT roll or the weapon is pulled from their grip, the rust monster will then stop and devour the weapon.

• To be honest I’m now struggling a bit for the last attack, any thoughts? It could use its tail to swipe at all adventurers within NEAR range, maybe?

STEP 13: FINISHING TOUCHES - I think it is pretty much done now but I think adding something to the description to fit it in with the setting would be good, I will see what I can do.

I will post up next week.