The Hand of Fate is a wondrous magical prosthetic limb designed for use in a Dungeons & Dragons 5th Edition campaign. It is an artifact that grows in power as the wielder collects and assembles the remaining fingers. Presented below are the mechanics and stats for incorporating the Hand of Fate into your game. It is a fantastic way to dump reasonable amounts of lore and has a built in mechanism for hiding information. A lot of random properties scattered throughout, and the ability to add this any setting makes it a big win. 

The Hand of Fate functions as a prosthetic arm when attached to a user. As each additional finger is added, the functionality of the hand increases, granting additional powers and abilities. When the arm is not holding a shield, it can function as one for calculating your AC. 

Not Quite Sentient. Each Finger of Fate has an Intelligence of 18, with a + 6 to Arcana, History, Medicine, Nature and Survival (Intelligence) checks; the DM decides which fingers have which skill proficiency, respectively. It can speak one of the languages of their wielder, but only answers interrogatives and will not respond to any other sentences directed to it. It can hear anything its user can hear, but only responds to questions from its user. For things that the Finger of Fate does not know or understand, it will take a moment to emphasize that additional fingers increases its usefulness. 

Hand of Fate Stages

As the wielder collects and attaches additional fingers, the Hand of Fate goes through the following stages, each providing the wielder with increased abilities:

Stage 1: One Finger

• The prosthetic arm can perform basic tasks and manipulate objects, but it is not yet suitable for combat or spellcasting.
• It has one Minor Beneficial Property (rolled from the table in the DMG or chosen by the DM).

Stage 2: Two Fingers

• The prosthetic arm gains the ability to wield a light weapon or cast spells with somatic components, but with disadvantage on attack rolls and ability checks that use Strength or Dexterity.
• It has one additional Minor Beneficial Property (rolled from the table in the DMG or chosen by the DM).

Stage 3: Three Fingers

• The disadvantage on attack rolls and ability checks that use Strength or Dexterity is removed.
• The wielder can use the arm to make an additional unarmed strike as a bonus action during their turn. This unarmed strike deals 1d4 + Strength modifier bludgeoning damage.
• It has one additional Minor Beneficial Property (rolled from the table in the DMG or chosen by the DM).

Stage 4: Four Fingers

• The wielder gains a +1 bonus to attack and damage rolls made with weapons wielded by the prosthetic arm.
• The wielder gains the ability to use the prosthetic arm to perform the somatic components of spells even if both hands are occupied.
• It has one additional Minor Beneficial Property (rolled from the table in the DMG or chosen by the DM).

Stage 5: Five Fingers

• The wielder gains a +2 bonus to attack and damage rolls made with weapons wielded by the prosthetic arm.
• The prosthetic arm can be used to cast the "Sending" spell once per day, with no spell slots or material components required. The spell save DC is determined by the wielder's spellcasting ability modifier.
• It has one additional Major Beneficial Property (rolled from the table in the DMG or chosen by the DM).

Special Properties

The Finger of Fate has the following special properties:

• Enhanced Durability: The crystal material is incredibly resistant to damage. The prosthetic arm has immunity to nonmagical damage and resistance to magical damage, and when it is not being used to hold a shield, it counts as one for calculating your AC.
• Attunement: To use the Finger of Fate, a character must first be unconscious while another creature uses a long rest to attach it to you. Requires the creature to be attuned to it to either have a missing limb or have one removed. 

Curse. Once attuned to the Hand of Fate, the wielder becomes obsessed with finding and attaching the remaining fingers. They have disadvantage on Wisdom (Insight) and Charisma (Persuasion) checks made against anyone who they believe has information about the location of the other fingers. This curse cannot be removed except by a "Wish" spell or by assembling all five fingers.

Shields require the Utilize action to Don or Doff. You gain the Armor Class benefit of a Shield only if you have training with it.

Notes: Inspired by Matt Colville, The Outer Limits, and a conversation with friends., creature missing an arm