The quick pitch: Rust Monster humanoid. If that idea sounds intriguing: I am attempting to play around with the homebrew feature and some of you do an excellent job. I think many of you who have more than 50 adds to your credit have done well. I have added a few that have achieved even higher, I have seen many homebrews that are terrible as I guess many of you might agree but to each-their-own, right?

I am writing as I have an idea I attempted to work on today and I failed tremendously when I forgot to hit save after 20 minutes of perfecting the description. I realized that I do not know the format anyway that most of you use quite well. I may attempt it again later but I admit I am frustrated with myself and wanted to see if any of you are interested in making it better than I could let me know. Otherwise, I am looking for suggestions on my ideas.

Essentially, I had the idea of a Variant-Human that was the result of a mad Wizard infusing a human with the rusting qualities of a Rust monster. Naturally, the main attribute of the "Rusty-Human" was the blessing and curse of being able to corrode metal rapidly. This naturally, made it difficult to use metal tools or weapons without gloves (the sweat contains a higher concentration of electrolytes that help in the rusting process.) I figured that a character wearing gloves still had a daily chance of destroying their own equipped weapons. Naturally, metal armor could not be worn. I determined that either the Rust Monster "Rust Metal" ability is good enough or perhaps modifying it to better fit a humanoid. I felt that a Rusty-Human could be resistant to attacks from metal weapons or perhaps damage is reduced by an amount equal to the constitution modifier of the character. I added that Adamantine weapons and armor could be both used or worn and also immune to the Rusty's ability. Lastly, I considered this to replace the Variant-Human feat. What are your thoughts? I am not so secretly hoping that one of you have achieved a +500 or higher in adds, might think this an intriguing race to create...thanks for reading. 

I would encourage you to make this race separate from humans. I think making it its own race will strengthen its identity.

Personally I worry about the Rust Metal ability as being very powerful. Maybe combine Rust Metal and Antennae into one trait where as an action you target one metal item. I would give a natural armor as well.

I think the Adamantine restriction is good, I would add magical items to that as well.

I strongly believe that as the person who came up with the idea, you should be the one to execute your vision, even if it doesn’t get as much attention (which I doubt will be the case).

Could you give me an idea of what a good trade-off would be for the OP concern of the Rust Metal ability? I have to admit I feel this way about several Race abilities like Yuan-Ti Magic Resistance and Poison Immunity...I felt the fact that the character not being able to wear metal armor or use metal tools/weapons was a good trade off. Should it be a once per short rest ability/reaction? Thank you for your help.

I would not suggest using the yuan-ti pureblood race as a comparison to homebrew. I agree with you, not being able to wear or wield nonmagical metal items sounds like a good trade off. I imagine instead of Rust Metal it's just Antenna which might look something like this.

Antennae.  As an action, you corrode a nonmagical ferrous metal object you 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 must make a Dexterity saving throw, against a DC equal to 8 + your (Dexterity? Strength? Constitution???) modifier + your proficiency bonus, to avoid your antennae.

If the object touched is either metal armor or a metal shield being worn or carried, it 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 takes a permanent and cumulative −1 penalty to damage rolls. If its penalty drops to −5, the weapon is destroyed

Quote from Astromancer >>

I would not suggest using the yuan-ti pureblood race as a comparison to homebrew. I agree with you, not being able to wear or wield nonmagical metal items sounds like a good trade off. I imagine instead of Rust Metal it's just Antenna which might look something like this.

Antennae.  As an action, you corrode a nonmagical ferrous metal object you 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 must make a Dexterity saving throw, against a DC equal to 8 + your (Dexterity? Strength? Constitution???) modifier + your proficiency bonus, to avoid your antennae.

If the object touched is either metal armor or a metal shield being worn or carried, it 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 takes a permanent and cumulative −1 penalty to damage rolls. If its penalty drops to −5, the weapon is destroyed

 I love your help and I hope you do not mind utilizing most of your suggestions and wording. You truly are very skilled in this (seen your work) and I look forward to finalizing my creation with your notes! Thank you.

Deleted...figured out my question.

I don't mind if you use my wording (I copied and pasted it from the rust monster to be perfectly honest). I'm glad I could help! I'd love to see the race when you're finished with it!

You were a big help and inspiration for it. I am a novice at homebrew but love the ability. I am sure there is a better way to share it but my limited skills force me to copy/paste link:

https://www.dndbeyond.com/subraces/112102-rusty-variant-human

I will again recommend making the race its own race.

I am not a fan of Corrosive Reaction. Especially how it targets a different group of materials (non-adamantine metal items) than Corrode (non-magical ferrous metal items). It also feels like redundant when you also have Corrode.

 I don't see the limitation on metal armor.

If you were to make this an actual race from this, I would give a +2 to Constitution and a +1 to Wisdom. Instead of Skill, I would give the rust monster's Iron Scent and a Natural Armor trait.

In an effort to make this a more acceptable homebrew, taking your suggestions seriously, I am working on it now. My lack of experience with using the tool set has hindred me, however, my experience with character creations has helped in creating the idea that is stuck in my head. I mention this as I am not sure why the reaction is troubling? Also, I copy-pasted your information that you gathered from the Rust Monster, but I added the Adamantine and magical weapon detail later. I see that a few things needed to be adjusted, and I should have looked more closely at the copy/pasting. However, in the details section of the creation, I mention that Adamantine is immune, magical items have advantage and I mention that: "typically can not wear armor or use metal weapons or tools." I said "typically" because I assumed that if a character found Adamantine armor or weapons they could utilize them. I will fix these issues as best I can with my new race as you suggested and will share it again to see what you think. I greatly appreciate your help. (I am going to remove the antennae. I think if I were to make a variant of this race I would make it as though it was a less evolved magically infusion giving it more of a Rust Monster appearance, as I can see how easy it would be to morph a Rust monster and a humanoid together.) Thank you again...

I'm glad I could help!

If you need help with the homebrew editor, don't be afraid to reach out. James Introcaso did a Design Workshop on making homebrew races in DDB. It could be helpful to take a look.