Sources
CR
Type
Size
Alignment
Movement

Tempest Spirit

Huge Undead, Chaotic Evil

Armor Class 12
Hit Points 195 (17d12 + 85)
Speed 0 ft., fly 60 ft. (hover)
STR
24
+7
DEX
14
+2
CON
20
+5
INT
16
+3
WIS
18
+4
CHA
19
+4
Saving Throws CON +10, INT +8, WIS +9, CHA +9
Skills Arcana +8, Perception +9
Damage Resistances cold, necrotic, poison; bludgeoning, piercing, slashing, from nonmagical attacks
Damage Immunities lightning, thunder
Condition Immunities Charmed, Exhaustion, Frightened, Grappled, Paralyzed, Petrified, Poisoned, Prone, Restrained
Senses passive Perception 19
Languages Common, Giant
Challenge 15 (13,000 XP)

Traits

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

Legendary Resistance (3/Day). If the spirit fails a saving throw, it can choose to succeed instead.

Actions

Multiattack. The spirit makes two Lightning Fist or Hailstone attacks in any combination.

Lightning Fist. Melee Weapon Attack: +12 to hit, reach 10 ft., one target. Hit:25 (4d8 + 7) lightning damage.

Hailstone. Ranged Weapon Attack: +12 to hit, range 90/180 ft., one target. Hit:17 (3d6 + 7) bludgeoning damage plus 7 (2d6) cold damage.

Death Bolt (Recharge 5–6). The spirit hurls a magical lightning bolt in a 120-foot line that is 10 feet wide. Each creature in that area must make a DC 18 Dexterity saving throw, taking 27 (6d8) lightning damage plus 16 (3d10) necrotic damage on a failed save, or half as much damage on a successful one. On a success or failure, an affected creature's hit point maximum is reduced by an amount equal to the necrotic damage taken. This reduction lasts until the creature finishes a long rest. The creature dies if its hit point maximum is reduced to 0.

Bonus Actions

Hailstorm (Recharge 4–6). The spirit conjures a hailstorm in a 20-foot-radius, 40-foot-high cylinder centered on a point it can see within 120 feet of itself. Each creature in that area must make a DC 17 Dexterity saving throw. On a failed save, a creature takes 10 (3d6) bludgeoning damage plus 10 (3d6) cold damage and has the prone condition. On a successful save, a creature takes half as much damage only.

Lore

A storm giant can escape death through a mystical ritual that transforms the giant into a semiconscious storm. However, if the giant performs the ritual in a place where the barrier between the Material Plane and the Shadowfell is thin, the seeping negative energy drastically alters the ritual's outcome. The giant's soul becomes infused with negative energy and doesn't disperse into the elements. Rather, it absorbs the elemental energy around it, and its lower body becomes a storm cloud. The…