Sources
CR
Type
Size
Alignment
Movement

Nyssa Otellion

Medium Fiend (devil, wizard), Lawful Evil

Armor Class 19 (natural armor)
Hit Points 202 (27d8 + 81)
Speed 30 ft., fly 50 ft.
STR
15
+2
DEX
14
+2
CON
17
+3
INT
22
+6
WIS
23
+6
CHA
18
+4
Saving Throws INT +12, WIS +12
Skills Arcana +12
Damage Resistances cold; bludgeoning, piercing, slashing, from nonmagical attacks that aren't silvered
Damage Immunities fire, lightning, poison
Condition Immunities Poisoned
Senses darkvision 120 ft., passive Perception 16
Languages Draconic, Infernal, telepathy 120 ft.
Challenge 17 (18,000 XP)

Traits

Devil's Sight. Magical darkness doesn't impede Nyssa's darkvision.

Magic Resistance. Nyssa has advantage on saving throws against spells and other magical effects.

Spellcasting

Spellcasting. Nyssa casts one of the following spells, using Intelligence as the spellcasting ability (spell save DC 20):

At will: disguise self, mage hand, minor illusion

2/day each: charm person, dispel magic, greater invisibility, wall of force

Actions

Multiattack. Nyssa makes three Bite or Lightning Strike attacks.

Bite. Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit:13 (2d10 + 2) piercing damage plus 14 (4d6) lightning damage.

Lightning Strike. Ranged Spell Attack: +12 to hit, range 120 ft., one target. Hit:36 (8d8) lightning damage.

Bonus Actions

Teleport. Nyssa teleports, along with any equipment it is wearing or carrying, up to 30 feet to an unoccupied space that it can see.