Gem Greatwyrm

Gargantuan Dragon (Gem), Typically Neutral
Armor Class 21 (natural armor)
Hit Points 507 (26d20 + 234)
Speed 60 ft., burrow 60 ft., fly 120 ft. (hover), swim 60 ft.
STR
28 (+9)
DEX
14 (+2)
CON
29 (+9)
INT
30 (+10)
WIS
24 (+7)
CHA
25 (+7)
Saving Throws Dex +10, Con +17, Wis +15, Cha +15
Skills Arcana +26, History +18, Perception +15
Damage Immunities force (amethyst), necrotic (topaz), psychic (emerald), radiant (crystal), or thunder (sapphire)
Condition Immunities charmed, frightened, poisoned, prone
Senses truesight 120 ft., passive Perception 25
Languages Common, Draconic
Challenge 26 (90000 XP)     Proficiency Bonus +8
Gem Awakening (Recharges after a Short or Long Rest).
Legendary Resistance (4/Day).
Unusual Nature.
ACTIONS
Multiattack.
Bite.
Claw.
Breath Weapon (Recharge 5-6).
Mass Telekinesis (Gem Awakening Only; Recharges after a Short or Long Rest).
Spellcasting (Psionics).
BONUS ACTIONS
Change Shape.
Psychic Step.
LEGENDARY ACTIONS
Claw.
Psionics (Costs 2 Actions).
Psychic Beam (Costs 3 Actions).

This full creature's stat block is not available (not OGL).

Fizban“s Treasury of Dragons
Gem Greatwyrm