I've homebrewed a rather cool item (in my opinion). The idea behind it is it can substitute for a shield and weapon, allowing the character two free hands while still being considered armed. It has several drawback mechanics to balance out the benefits. And of course, it requires you to cut off your own arm in order to use it in the first place.
Arm of Wrought Iron (requires attunement)
A prosthetic arm powered by magic, it is a cold, dark, metallic arm that serves offensive and defensive purposes. You can use this arm in place of one of your own arms. When wielding this item, you gain the following benefits:
- You can use this arm normally, as if it was your own; you do not feel pain through this arm
- Your Strength score increases by 1 (maximum of 20)
- You have +1 to AC and are considered wearing a shield
- You have +1 to hit on attack rolls with this arm and are considered wielding a one-handed heavy weapon
- Your unarmed strikes with this arm deals 1d6+1 bludgeoning damage
In addition, it has the following side effects:
- You take 1d4 more damage from lightning damage
- If you drop to 0 HP while attuned to this item, it becomes unattuned to you
- This item automatically attunes to you if you have at least half your hit points
- You do not need a short or long rest to attune to this item
I considered what the damage die should be. A d4 would put it at par with an improvised weapon, which I thought would not be in line with the item's purpose (to discourage the character to wield a weapon in this hand), so I upgraded it to a d6. The +1 damage simulates a magical weapon of at least uncommon rarity.
The weird attunement mechanics are meant to give this item a serious risk if used, which hopefully balances out all its benefits. When unattuned, this arm becomes a limp hunk of metal until enough HP is regained to attune to it again. Thematically, this is the arm breaking due to wear and tear, and subsequently being repaired back to a functional level.
Having said all that, what should the rarity level of the above item be?
Does the wearer have to amputate their arm to use this item, Vecna style?
What happens if you wear a shield?
- Choose from the +2 of the shield or the +1 from the arm, not both, because: PHB pg. 144 You can benefit from only one shield at a time