Missing Arm or Hand
You are missing a hand or partial forearm (IE 1), hand and partial forearm or entire forearm (IE 2), entire forearm and hand (IE 3), or entire arm and hand (IE 4). You are unable to use 2-handed weapons, a second weapon or shield, or anything else requiring two hands without a prosthesis. (If you are missing part of your arm but not your hand, you can still use a shield but not a two-handed weapon.) You have a −(IE) penalty on Strength (Athletics) checks that require two hands, such as climbing, and in mounted combat, whenever you attack or take damage, you need to succeed on a DC 8 Dexterity saving throw or fall off your mount.
Real-world Examples
Symbrachydactyly, Congenital Amputation
Assistive Options
An artisan can make prosthetic hands and arms for various purposes, with differing durability, function, and price. The base cost of a cosmetic wooden replacement is (5 + (IE)) × 50 gp, with costs increasing significantly for specialized uses. It must also be adjusted or replaced annually or when you experience any major physical changes. A prosthesis designed to hold a weapon will still have a penalty of −(IE) on attack rolls with that hand due to the prosthesis’s lack of feeling and fine motor control.
1d10 of your fingers bend in odd directions, curving sideways or even backwards. (Roll 1d10 for the number of fingers, then 1d10 for each to determine which finger.) Depending how many fingers are diversely shaped from each hand, you have penalties to any action using your hands. The GM should determine the penalties but can use −1 per 2 fingers on each hand. Each atypically shaped thumb gives a −1 penalty itself. If most or all of your fingers curve backwards, you may be mistaken for a 
You are missing 1d10 fingers. (Roll 1d10 for the number of fingers, then 1d10 for each to determine which finger.) Depending how many fingers are missing from each hand, you have penalties to any action using your hands. The GM should determine the penalties but can use −1 per 2 missing fingers on each hand. Each missing thumb gives a −1 penalty itself.
1d10 of your fingers are longer than expected for your ancestry. This has no immediate game mechanic but will lead to confusion, fear, or other social effects, depending on the situation.
You have (IE) extra fingers on your hand(s). You have a +(IE) bonus to Dexterity (Sleight of Hand) checks and Charisma (Performance) checks to play fingered musical instruments. This may lead to confusion, fear, or other social effects, depending on the situation.
1 + (IE) of your fingers are fused together. This gives you a −(IE) penalty to Dexterity (Sleight of Hand) checks.
Your fingers end in claws or talons. This allows you to make an unarmed strength attack that does 2 (1d4) slashing damage. This also gives you a −(IE) penalty on Dexterity (Sleight of Hand) checks.
1d10 of your fingers are smaller and weaker than expected. (Roll 1d10 for the number of fingers, then 1d10 for each to determine which finger.) Depending how many fingers are undergrown from each hand, you have penalties to any action using your hands. The GM should determine the penalties but can use −1 per 2 undergrown fingers on each hand. Each undergrown thumb gives a −1 penalty itself.
Your fingers are webbed and give you advantage on Strength (Athletics) checks on swimming. This also gives you a −(IE) penalty to Dexterity (Sleight of Hand) checks. Note: In the real world, human webbed digits do not give swimmers any noticeable benefits.)