Sources
CR
Type
Size
Alignment
Movement

Deathless Rider

Medium Undead, Lawful Evil

Armor Class 18 (chain mail, shield)
Hit Points 84 (13d8 + 26)
Speed 20 ft.
STR
18
+4
DEX
10
+0
CON
14
+2
INT
6
-2
WIS
6
-2
CHA
5
-3
Saving Throws STR +7, CON +5
Skills Athletics +7, Perception +1
Damage Resistances necrotic
Damage Immunities poison
Condition Immunities Exhaustion, Poisoned
Senses darkvision 60 ft., passive Perception 11
Languages understands the languages it knew in life but can't speak
Challenge 5 (1,800 XP)

Traits

Mounted Adept. While mounted and without the incapacitated condition, the rider has advantage on melee attack rolls against any unmounted creature smaller than its mount, the rider and its mount have advantage on Dexterity saving throws, and the rider can force an attack targeted at its mount to target the rider instead.

Undead Fortitude. If damage reduces the rider to 0 hit points, it must make a Constitution saving throw with a DC equal to 5 + the damage taken, unless the damage is radiant or from a critical hit. On a success, the rider drops to 1 hit point instead.

Actions

Multiattack. The rider makes two Axe attacks. It can replace one of these attacks with Fell Glare.

Axe. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit:13 (2d8 + 4) slashing damage.

Fell Glare. The rider gazes at a creature within 30 feet of itself. The creature must succeed on a DC 13 Wisdom saving throw or have the frightened condition for 1 minute. The frightened creature can repeat the saving throw at the end of each of its turns, with disadvantage if it can see the rider, ending the condition on itself on a success.

Lore

Legends told in the courts of Eldraine suggest that the deathless riders serve a warlock-queen, known simply as the Shadow Queen, who rules from a castle called Dynnistan. It isn't known whether these legends are based on any true experience or are simply the result of imagination trying to account for a terrifying and unexplained phenomenon.