Great Crystal (5e Creature)
From D&D Wiki
Huge elemental (shardling), lawful good
Skills Arcana +11, History +11
Innate Spellcasting (Psionics). The great crystal's innate spellcasting ability is Intelligence (spell save DC 16, +8 to spell attacks). The great crystal can cast the following spells innately, requiring no material components:
At will: blur, guiding bolt, light, mage hand (the hand is invisible), meld into stone, minor illusion, tongues
Immutable Form. The great crystal is immune to any spell or effect that would alter its form, except for its Reshape.
Psionic Ward. The AC of the great crystal includes its Wisdom bonus.
Psionic Absorption. Whenever the great crystal is subjected to psychic damage, it takes no damage and instead regains a number of hit points equal to the psychic damage dealt.
Reshape. The great crystal can use its action to change its physical appearance into any form of its choice. The great crystal may not change its size or composition, so it may not become a Tiny crystal, but it may, for example, become a long chain of crystal that could fit into a space large enough for a Tiny creature.
Sense Thoughts. The great crystal senses thoughts within 120 feet of it at will. This trait otherwise works like the detect thoughts spell but isn't itself magical.
Multiattack. The great crystal makes three attacks.
Slash. Melee Weapon Attack: +6 to hit, reach 10 ft., one target. Hit: 13 (3d6 + 3) slashing damage.
If a swarm of shardlings grows to immense size, the tiny crystals that make it up begin to fuse together. The resulting massive crystal is called a great crystal. Each shardling retains its knowledge and personality, but it also learns everything that any other shardling within the great crystal knows. The great crystals are among the most powerful psionics among shardlings, with the power to bar certain kinds of creatures from their territories, the power to telepathically link creatures, and the power of teleportation. Though the great crystal is fused together, it can just as easily reshape itself.
Elemental Nature. A great crystal doesn't require air, food, drink, or sleep.