Voidplate

Monster

At a glance

What it is: A suit of star-black plate armour, eight feet tall, still marching long after the knight inside it died in the dark between the stars.
Where it's found: Fallen-star craters, sky-wreck ruins, and at the bottom of anything that fell from very high up.
What it wants: To finish its last order. It no longer remembers what that order was, so it guards whatever ground it is standing on.
Challenge: 8. A hard fight for four characters of 5th to 7th level.

Read aloud

The crater is silent. Not quiet, silent: your boots make no sound on the glass, and when you call to your friend your voice goes nowhere. In the middle of it stands a knight in black armour, perfectly still, frost crawling across its plates. Its visor is open. There is nothing inside but stars.

How to run it

The Voidplate never charges. It walks, steady and unhurried, and lets the silence do the work: spellcasters inside its hush can't cast anything that needs words, so make them choose between staying close and staying useful.

Save Seal the Breach for when the party bunches up around it. The cold leaves them unable to react, and that is when the greatsword comes down.

How to beat it

Crack the seal. Radiant damage shows a thin line of light at its collar. A creature next to it can use an action to pry the gorget open with a DC 15 Strength check, and the Voidplate loses its cold immunity until the start of its next turn.
Give it new orders. A whispered command in the old knightly cant (DC 16 Charisma check) makes it stand down for one minute while it thinks about it.
Leave its ground. It never follows anyone past the rim of its crater.

Voidplate stat block

D&D 5e · CR 8

Armor Class: 19
Hit Points: 136
Challenge: 8
Proficiency bonus: +3
Passive Perception: 15

Ability modifiers
STR	DEX	CON	INT	WIS	CHA
20 (+5)	10 (+0)	18 (+4)	12 (+1)	14 (+2)	8 (-1)

Saving throws CON +7, WIS +5

Skills Athletics +8, Perception +5

Damage resistances necrotic

Damage immunities cold, poison

Senses darkvision 120 ft.

Languages understands Common but can't speak

Traits

Nobody Home. The armour is empty. It doesn't breathe, eat or sleep, and it can't be charmed, frightened or poisoned. Poison damage does nothing to it.

Hush of the Deep Dark. Sound dies within 15 feet of the Voidplate, as it did in the dark between the stars. Creatures there can't speak above a whisper, and spells with a verbal component can't be cast there.

Attacks

Starforged Greatsword. Melee attack, +8 to hit, 2d6+5 slashing damage.

Gauntlet Lance. Ranged attack, +8 to hit, 3d10 force damage.

Actions

Seal the Breach (Recharge 5-6). The Voidplate vents the cold of empty space in a 30-foot cone. Each creature there makes a DC 16 Constitution saving throw, taking 6d8 cold damage on a failure or half as much on a success. A creature that fails can't take reactions until the start of its next turn.