Sources
CR
Type
Size
Alignment
Movement

Gray Slaad

Medium Aberration (shapechanger), Chaotic Neutral

Armor Class 18 (natural armor)
Hit Points 127 (17d8 + 51)
Speed 30 ft.
STR
17
+3
DEX
17
+3
CON
16
+3
INT
13
+1
WIS
8
-1
CHA
14
+2
Skills Arcana +5, Perception +7
Damage Resistances acid, cold, fire, lightning, thunder
Senses blindsight 60 ft., darkvision 60 ft., passive Perception 17
Languages Slaad, telepathy 60 ft.
Challenge 9 (5,000 XP)

Traits

Shapechanger. The slaad can use its action to polymorph into a Small or Medium humanoid, or back into its true form. Its statistics, other than its size, are the same in each form. Any equipment it is wearing or carrying isn't transformed. It reverts to its true form if it dies.

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

Magic Weapons. The slaad's weapon attacks are magical.

Regeneration. The slaad regains 10 hit points at the start of its turn if it has at least 1 hit point.

Spellcasting

Innate Spellcasting. The slaad's innate spellcasting ability is Charisma (spell save DC 14). The slaad can innately cast the following spells, requiring no material components:

At will: detect magic, detect thoughts, invisibility (self only), mage hand, major image

1/day: plane shift (self only)

2/day each: fear, fly, fireball, tongues

Actions

Multiattack. The slaad makes three attacks: one with its bite and two with its claws or greatsword.

Bite (Slaad Form Only). Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit:6 (1d6 + 3) piercing damage.

Claws (Slaad Form Only). Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit:8 (1d10 + 3) slashing damage.

Greatsword. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit:10 (2d6 + 3) slashing damage.

Lore

In the Ever-Changing Chaos of Limbo, bits of forest and meadow, ruined castles, and isolated islands drift through a tumult of fire, water, earth, and wind. The foremost inhabitants of this inhospitable plane are the toad-like slaadi. Slaadi are undisciplined and have no formal hierarchy, although weaker slaadi obey stronger ones under threat of annihilation.