Adamantine Strongbox

Wondrous item (mundane, very rare)
Crafted by a duergar master-smith

This squat, brutal coffer is forged from overlapping adamantine plates, pressure-fitted and rune-scored with dwarven structural glyphs. The interior smells faintly of oil, ash, and hot stone.

Object Statistics

Size: Medium object (20cm×20cmx20cm)
Weight: 15 kg
Material: Adamantine
Armor Class AC 23
Hit Points HP 90
Damage Threshold 12

Damage Resistances

• Bludgeoning, Piercing, Slashing from nonmagical attacks

Damage Immunities

• Poison
• Acid (nonmagical only)

Condition Immunities

• Charmed
• Frightened
• Exhaustion

Special Traits

Adamantine Construction

The box is immune to critical hits and ignores any feature that exploits weak points in objects (such as Siege Monster traits relying on precision).

Dwarven Pressure Seal

• The lid seals airtight and watertight when closed.
• Contents are protected from:
  
  
• Spores and fungi
• Smoke and toxic vapors
• Underdark humidity and corrosion
  
  

Compression Reversion

Якщо істота всередині кейсу намагається повернутися до свого справжнього розміру (через завершення Polymorph, втрату концентрації або подібний ефект), активується компресійний механізм.

• Істота отримує 10d10 force damage
• Кидає CON saving throw проти DC заклинача
• Успіх: половина шкоди і виривається з коробки
• Провал: повна шкода та стан restrained до кінця її наступного ходу
• Кейс отримує 4d6 шкоди, якщо істота виривається з коробки

Якщо кейс знищений, істота негайно виходить назовні, займаючи найближчий вільний простір.

Reinforced Forge Hinges

The hinge cannot be targeted or damaged separately unless the box is already reduced below half HP.

Lock & Access (PC-Crafted)

Integrated Lock

• DC 18 Dexterity (Thieves’ Tools) to pick
• DC 23 Strength (Athletics) to force open
  
  
• Failing either by 5 or more produces a loud metallic clang audible to 60 ft
  
  

Maker’s Tolerance (Important)

Because the PC forged it:

• The PC has advantage on checks to open, repair, or modify the box
• The PC can open it as an object interaction, even under stress
  
  

Interaction with Magic

• Detect magic: No aura
• Heat metal: The box becomes hot but takes no damage; contents are unharmed
• Shatter: Deals half damage automatically
• Knock: Opens the box for 1 round, suppressing the seal
• Disintegrate: Destroys the box outright (no save)
  
  

Crafting Legacy Traits (PC-Specific)

These traits exist only because a duergar PC made it.

Forge Memory

If the PC is within 30 ft of the box, they instinctively know:

• Whether it has been opened
• Whether it has been damaged
• Whether its contents have been disturbed

(No action required; this is passive.)

Structural Insight

Once per long rest, the PC can:

• Reduce damage dealt to the box by 10 from a single source
  (Reaction; represents instinctive reinforcement or positioning.)