Scion of the Living Arm Martial Archetype

Bound by blood and instinct, a Scion of the Living Arm is a fighter who has not merely found a weapon, but formed a symbiotic bond with a living, shapeshifting mimic. This creature — your mythic arm — feeds on your victories, adapts to your foes, and grows with you, merging monstrous hunger with masterful skill. Where others see a blade, you know the truth: it is a mind, a mouth, and a heart — and it beats with yours.

3rd Level: Symbiotic Weapon

Living Arm

• Your mythic arm counts as magical for overcoming resistance and immunity to nonmagical attacks and damage.
  
  
• It cannot rust, dull, or break, and you have advantage against being disarmed of it while conscious. This weapon cannot be used against you.
  
  
• If separated, you know the direction and plane it resides on, and its movement direction.                     l
• Awareness: Your mythic arm is conscious and aware of its surroundings when you are. It has a basic sentience (STR 17, DEX 12, CON 15, INT 12, WIS 14, CHA 8), understands your languages, and can communicate with you telepathically within 60 feet. Movement speed of 20ft.
  
  
• You can absorb enchantments from magical weapons. After spending one hour with a magic weapon (that you are able to attune to), you can transfer its enchantment into your mythic arm, causing the original weapon to lose its magic. You can change your mythic arm into the form of any weapon whose enchantment you have absorbed by concentrating for one hour.

Feeding Frenzy

When you reduce a hostile creature to 0 hit points using your mythic arm, regain hit points equal to your proficiency bonus + your Strength or Dexterity modifier (your choice). If the creature was Huge or larger, regain double that amount.

Magical Imitation

When a creature you can see within 60 feet casts a spell of 1st level or higher that deals damage or imposes a harmful condition, you can use your reaction to capture a fragment of that magic into your mythic arm.

• You can store one magical imitation at a time, lasting until the end of your next turn.
  
  
• On your next melee attack hit with the mythic arm, you may unleash the imitation:
  
  
• Damage Spells: Deal an additional 1d6 damage of the captured spell’s damage type.
  
  
• Control Spells: The target must succeed on a Constitution saving throw (DC = 8 + proficiency bonus + Strength or Dexterity modifier) or have its speed halved and be unable to take reactions until the start of your next turn.
  
  

You can use this feature a number of times equal to your proficiency bonus per long rest.

7th Level: Hungry Arm

Mimic Property

At the end of a long rest, choose one property for your mythic arm: finesse, light, reach, or thrown (20/60 ft.).

Tendril Grab

Additionally, once per turn when you hit a creature with your mythic arm, as a bonus action you can cause barbed tendrils to erupt:

• The target must succeed on a Strength saving throw (DC = 8 + proficiency bonus + Strength or Dexterity modifier) or be grappled (escape DC same).
  
  
• While grappled this way, the target takes acid damage equal to your proficiency bonus at the start of its turn.
  
  

The tendrils retract if your mythic arm loses concentration (as if concentrating on a spell), if the grapple ends, or if you release the target (no action). You cannot concentrate on multiple people at the same time with this grapple.

10th Level: Adaptive Flesh

Imitation Adept

Your mythic arm adapts to threats faster.

• You can store up to two magical imitations at once.
  
  
• When you hit with an attack, choose which imitation to unleash.
  
  
• If you use Action Surge, you can unleash a stored imitation on each attack made during the surge.
  
  
• The extra damage from Magical Imitation increases to 2d6.
  
  

Predator's Instinct

When you hit a creature, you can choose one trait to gain until the end of your next turn:

• Natural Armor: +1 bonus to AC.
  
  
• Hunter’s Reflexes: Advantage on your next attack roll.
  
  
• Predator's Leap: Your jump distance is doubled.
• Extend: Gain +10 feet reach on your attacks.
  
  

You can use this adaptation feature a number of times equal to your proficiency bonus per long rest.

15th Level: Voracious Bond

Aggressive Partner

Your mythic arm is a full partner in battle. When you use your Action Surge, your mythic arm lashes out wildly:

• Immediately after you Action Surge, you can make a free melee attack with your mythic arm against a creature within reach.
  
  
• Additionally, if you kill a creature with your mythic arm, you can immediately make another melee attack as a reaction.

Devour Magic

Once per long rest, when targeted by a spell of 3rd level or lower, you can use your reaction to devour the magic:

• The spell automatically fails against you.
  
  
• You immediately store a magical imitation from it without expending a magic imitation slot.
  
  

Additionally, your Feeding Frenzy improves:
When you slay a creature with your mythic arm, you gain temporary hit points equal to your Fighter level.

18th Level: Perfect Predator

We Are One

You and your living arm move as one.

• Whenever you make an attack roll after using your Action Surge, treat rolls of 9 or lower as a 10.
  
  
• These attacks cannot be made with disadvantage.
  
  
• When you roll initiative and have no uses of Action Surge remaining, regain one use.
• Whenever you use your Action Surge, you can also activate 1 predator's instinct ability (Natural Armor, Hunter’s Reflexes, Predator's Leap, Extend). (This is always active during combat but requires concentration)
  
  
• Attacks made by your mythic arm score a critical hit on a 19–20.
  
  

Additionally, while under Action Surge, attacks deal an extra 3d6 damage of your stored imitation’s damage type.