Crystal Cluster

Earth Glide: The Crystal Elemental can burrow through nonmagical, unworked earth and stone. While doing so, the Crystal Elemental doesn't disturb the material it moves through.

Reverbertating Crystal: Whenever the Crystal Elemental is affected by a sound based effect the effect is recast centered on it with in all directions with its range halved and only once per attack or effect.

The Crystal Elemental is not immune to these effects however.

Magic Resistance: The Crystal Elemental has advantage on saving throws to avoid spells and spell like effects.

Magic Reflection: Whenever the Crystal Elemental is affected by a spell of 6th level or lower the caster must roll a d6, on a 4 or 5 the spell fails to affect the Crystal Elemental on a 6 the spell is reflected towards the caster, being recast targeting it or with it as the center of the spell area if possible.

Radiance Surge: Whenever the Crystal Elemental would take radiant damage it instead reflects that damage (this effect hapens before damage calculation ignoring effects that would ignore resistance or immunity to radiant damage), all creatures within 15ft of the Crystal Elemental must succeed in a DC 16 Constitution saving throw taking radiant damage equal to half of the damage that would have been dealt to the Crystal Cluster instead.

Immutable Form: The Crystal Elemental is immune to effects that would alter its form such as the polymorph spell.

Crystal Heart: The Crystal Cluster flows with gravitational energies, it has two forms, Retracted and Expanded, it changes betwen this forms at the start of its turn.

Multiattack: The Crystal Cluster makes three attacks or two attack and uses one of its available actions on its attack action.

Reflection Nova (Only if Expanded): All creatures within 30ft of the Crystal Cluster must succeed in a DC 16 Constitution saving throw taking 4d6 radiant damage on a failure, half as much damage on a success.

Crystaline Slam: Melee Weapon Attack +9 to hit, 5ft reach, one target, for 2d6+5 bludgeoning damage + 1d6 slashing damage.

Reflection Beam (Recharge-6 or otherwise if it would take radiant damage): All creatures within a 60ft long 5ft wide line centered on the Crystal Cluster must succeed in a DC 16 Dexteirty saving throw taking 4d6+5 radiant damage on a failure.

Expand: All creatures wtihin 15ft of the Crystal Cluster must succeed in a DC 16 Strength saving throw taking 2d6 slashing damage and bieng pushed 10ft away from the Crystal Cluster on a failure.

The Crystal Cluster takes damage equal to the damage dealt by this shrapnel of crystal (it cannot be reduced in any way)

Retract: All creatures within 15ft of the Crystal Cluster must succeed in a DC 16 Strenght saving throw being pulled 10ft near the Crystal Cluster on a failure.

Furthermore the Crystal Cluster regains 2d6 hit points.

Crystal Shrapnel (Only if Retracted): Whenever the Crystal Cluster takes damage all creatures within 5ft of it must succeed in a DC 16 Dexterity saving throw taking 2d6 slashing damage on a failure.