Rust Monster Animal Companion

[BranMan]

Hi Playground,

In the game that I'm running, the PCs found a rust monster and fed it lots of metal that they had on hand, and the ranger rolled a natural 18 on his handle animal check to make it friendly. They had just made it to level 3, and the ranger had not yet found an animal companion. He wanted to have the rust monster, (who they named roomba) be his companion, which obviously doesn't work by RAW (not a beast, cr 1/2) but could be very interesting. I'm ruling that they have to feed it a good amount of metal each day for it to stay friendly, and I was considering not granting it the ranger's prof. bonus to everything as normal.

Any thoughts on balance, or how I should go about this? I also haven't decided if the ranger should be allowed to use his action to command the rust monster to use its rust metal ability.

[SouthpawSoldier]

AFB, so I have limited helpful input. Posting mainly to subscribe to this thread.

However, I have to say you should do anything you can to keep this going, just to reward ingenuity.

[Joe the Rat]

Likewise codex-challenged, but here goes.

How do the rest of the players feel about it? That's kind of key. If they think it's funny/clever/awesome then you probably don't have to tweak too much. But be prepared for others to want something out-of-the-ordinary.

Ignore the CR for a minute. How does a Rust Monster stack up compared to, say, a wolf? If it's overall tougher, then you may need an adjustment. If they're fairly comparable, I'd be more inclined to take the Wimpy approach ("I will gladly pay you Tuesday for a hamburger today") and simply borrow power from later levels. Rusty starts standard (or with lower HD if beefiness is way off) and doesn't scale up until "normal" animal companions would catch up.

The challenge is going to be the rust attack. I feel like not having that misses half the "fun" of it, but that could make it to where you easily chew through your humanoid opponents (while doing nothing against "monsters")... but it also starts eating into your profits. What Rusty touches cannot be resold. My first thought would be to make it uncontrolled by the Beastmaster, at least initially. On the attack command, If the opponent has a significant amount of metal, Rusty has an X% chance of attempting a rust attack rather than whatever else it is they do. As this is not your ordinary creature, having greater difficulty controlling your companion initially might be warranted. Poorer rolls (as you've suggested), small chance of not following commands, tendency to stop and chow down after getting a particularly tasty bit of metal, etc. Nothing that completely gimps it, but adds a little difficulty early on.

Plus you get all the RP joy of traveling with a walking oxidizer. Knightly orders are NOT going to be happy to see you. Also make sure it's getting a well-balanced diet. Did you know Rust Monsters need to consume 4 oz. of copper a week to maintain their immune systems? :smallwink:

[Kyutaru]

Considering only NPCs really use armor, it's actually not that big a deal. The 5th edition Rust Monster is much weaker than his past editions, which Warforged have come to fear as 'El Laranja Diablo'.

The new Rust Metal doesn't affect magical items at all, only affects weapons that actually strike the rust monster, and when making a rust antenna attack against a weapon or armor held by a creature the creature is allowed a DC 11 Dexterity save to avoid the attack.

Additionally, armor hit by the attack only reduces in armor class by -1 until it hits AC 10 and is destroyed. Weapons rusted just suffer a permanent -1 damage reduction. Both of these are cumulative effects but shouldn't make the entire item completely worthless to sell. Just significantly reduced pay!

[BranMan]

yeah, the RM really isn't all that powerful, except for a nice 27 hp and decent armor. Its bite is the only attack it has, and it does very little damage as well. RP-wise, having the monster as a member of the party could be pretty entertaining. The RM has already tried to eat the ranger's only shortswords, and he already ate most of his arrowheads. Would giving a proficiency bonus to everything make the RM too strong? That would give it a +5 to hit, 1d8 +1 (or +3 if the ranger gives the bonus to damage as well, I forget), still no multiattack, and 16 AC. 40 foot movement speed is nice too, as the ranger is a halfling and could ride it. These are definitely not OP stats. And all of the metal-rusting shenanigans will probably hurt the party more than the monsters they face. How much metal do you think the RM would need per day to stay friendly?

[Kyutaru]

Well the rust monster actually eats rust that he creates from corroding metal objects. If the party can find some old rusted crap, they could feed him easily without hurting their wallets. I'd say he's like a dog and doesn't know when to stop eating. He can pig out on a suit of armor and be satisfied for a few days, but he needs at least a sword to stay well fed daily. If he's reduced to eating only a dagger per meal, he better be getting three meals a day or he's going to be mighty hungry. Arrows are like chips to him, great snacks.

[SouthpawSoldier]

Arrowheads could serve as training treats, as well.

All kinds of interesting inspirations from this.

[FadeAssassin]

"If they are well treated and well fed, they can also become friendly companions or pets"

This is the last sentence in the Rust Monster entry. So it seems to say (By lore at least) That a RM could be a Ranger's Companion.

[Kyutaru]

Any Ranger using a Rust Monster as a companion should become keenly affiliated with leather armor, bone arrowheads, yew longbows, and how to dual wield clubs.

[BranMan]

Any Ranger using a Rust Monster as a companion should become keenly affiliated with leather armor, bone arrowheads, yew longbows, and how to dual wield clubs.

Ooh, I can't wait to tell him that after his character sleeps, all of the studs have dissapeared from his armor :smallamused:

This will be amusing!

[Safety Sword]

You could make it (more) interesting by adding a small chance for the rust monster to become metal crazed after it consumes metal in combat. It may ignore its instructions. It would then turn to the nearest source of metal and try to eat it.

I would only do this if you see that the special ability is trivializing encounters. Otherwise if the power balance can be maintained it's a memorable pet for your ranger PC :smallcool:

[Slipperychicken]

Any Ranger using a Rust Monster as a companion should become keenly affiliated with leather armor, bone arrowheads, yew longbows, and how to dual wield clubs.

Just get a pair of those wooden swords with obsidian edges (Macuahuitil) which the Aztcs used. Or see if Ironwood is still a thing in 5e.

And don't forget stone. Spears, arrows, and axes can all be made with stone instead of metal.

[rlc]

the studs disappearing is a good idea. have it do other things like that, that you might expect a metal-eating dog to do. maybe even try to eat some of the ranger's gold and get sad that it can't.

[Kyutaru]

Ranger: "Good morning guys! Er, wait, why is my studded leather armor now just regular leather armor?"
Rogue: "What the- my daggers! They're just HILTS! How am I supposed to throw these???"
Warrior: "Ugh, that rust monster slept on my shield... or at least it WAS a shield."
Priest: "Has anyone seen my holy symbol?"
Mage: "Blasted monster! Those book bindings were centuries old!! I should polymorph you into a toad!"

[Vizzerdrix]

I support this idea.

[Santra]

After about a week of it being with them they wake up one morning to find that it made a nest in the backpack of one of the other characters (whichever one wears the most metal on them) and laid about a dozen eggs in said nest.

[Rysan Marquise]

Beastmaster is already a little weak, so the additional flexibility of allowing this should be fine.

Honestly, by my estimate, it can fully be treated as a Beastmaster companion without issue. It will be a little strong at first, but soon it will only be a minor advantage over other beasts.

[Person_Man]

I love it.

In fact, since the Ranger is mediocre/weak at mid-high levels, I think it makes a lot of sense to replace the Beastmaster's default Animal Companion with a Wild Empathy ability. You get free Proficiency and Expertise with Animal Handling at 3rd level (or Prof and/or Expertise in another Skill, if you already have either). If you can befriend a Beast, it becomes your temporary Companion. It aids and fights along side the Ranger. You can command it to do whatever as an Action, and it will continue to do so each round, but it only does so according to its nature and limited intelligence. And the Companion requires special care and treatment, or it will leave or turn against you. And as you gain levels and meet new Beasts, you can add more Companions (if they're relatively weak and could legitimately get along with each other) or say goodbye to your old Companion to get a more powerful one.

The only trick will be that you as a DM have to balance allowing the Ranger to have a really cool thing (which at the very least needs to be as cool as having Conjure Whatever or Animate Dead), without having the Ranger's Companion outshine the other players.

On the flip side, I would not punish the Ranger or the other players because he's playing his character and using his signature class ability in a fun and interesting way. Don't have the Rust Monster eat all their metal UNLESS they actively mistreat it or don't feed it for a couple of days. That just makes all of the players reluctant to be creative the next time they come across a Beast.