Sources
CR
Type
Size
Alignment
Movement

Ghostblade Eidolon

Medium Undead, Any alignment

Armor Class 12
Hit Points 55 (10d8 + 10)
Speed 30 ft.
STR
16
+3
DEX
15
+2
CON
12
+1
INT
13
+1
WIS
12
+1
CHA
14
+2
Skills Acrobatics +5, Athletics +6, Perception +4
Damage Resistances necrotic; bludgeoning, piercing, slashing, from nonmagical attacks
Damage Immunities poison
Condition Immunities Charmed, Exhaustion, Frightened, Grappled, Paralyzed, Petrified, Poisoned, Restrained
Senses passive Perception 14
Languages the languages it knew in life
Challenge 5 (1,800 XP)

Traits

Blurred Form. Attack rolls against the eidolon are made with disadvantage unless the eidolon is incapacitated.

Incorporeal Movement. The eidolon can move through other creatures and objects as if they were difficult terrain. It takes 5 (1d10) force damage if it ends its turn inside an object.

Turn Resistance. The eidolon has advantage on saving throws against any effect that turns undead.

Actions

Multiattack. The eidolon makes two ghostblade attacks.

Ghostblade. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit:8 (1d8 + 3) slashing damage plus 11 (2d10) force damage.

Lore

When a mortal soul traumatically sacrifices its identity in order to escape the Underworld as a Returned, its identity manifests as a spirit-like eidolon. While eidolons possess many of the skills and details related to their past lives, they're disconnected from those experiences, choosing to wander the world or brood in haunts they're drawn to in death. They care nothing for morbid reunions with their lost bodies or Returned remnants.