Sources
CR
Type
Size
Alignment
Movement

Green Slaad

Large Aberration (shapechanger), Chaotic Neutral

Armor Class 16 (natural armor)
Hit Points 127 (15d10 + 45)
Speed 30 ft.
STR
18
+4
DEX
15
+2
CON
16
+3
INT
11
+0
WIS
8
-1
CHA
12
+1
Skills Arcana +3, Perception +2
Damage Resistances acid, cold, fire, lightning, thunder
Senses blindsight 30 ft., darkvision 60 ft., passive Perception 12
Languages Slaad, telepathy 60 ft.
Challenge 8 (3,900 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.

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 12). The slaad can innately cast the following spells, requiring no material components:

At will: detect magic, detect thoughts, mage hand

1/day: fireball

2/day each: fear, invisibility (self only)

Actions

Multiattack. The slaad makes three attacks: one with its bite and two with its claws or staff. Alternatively, it uses its Hurl Flame twice.

Bite (Slaad Form Only). Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit:11 (2d6 + 4) piercing damage.

Claw (Slaad Form Only). Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit:7 (1d6 + 4) slashing damage.

Staff. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit:11 (2d6 + 4) bludgeoning damage.

Hurl Flame. Ranged Spell Attack: +4 to hit, range 60 ft., one target. Hit:10 (3d6) fire damage. The fire ignites flammable objects that aren't being worn or carried.

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.