Arcane Suppression Sentinel

Magic Absorption Aura.
The Sentinel emits a 30-foot radius anti-magic field that does not suppress magic entirely but redirects magic to power its core. Creatures within the field have disadvantage on spell attack rolls and saving throws to maintain concentration. Spells cast within this area trigger the Sentinel's Absorb Magic trait.

Absorb Magic.
When a creature casts a spell within 30 feet of the Sentinel, it gains temporary hit points equal to twice the spell's level and regains 1d6 hit points. If the spell is 3rd level or higher, the Sentinel gains advantage on its next attack roll made within 1 minute.

Immutable Form.
The Sentinel is immune to any spell or effect that would alter its form.

Anti-Caster Tactics.
The Sentinel has advantage on attack rolls against creatures concentrating on a spell or creatures that have cast a spell within the last round.

Multiattack.
The Sentinel makes two Slam attacks.

Slam. Melee Weapon Attack: +7 to hit, reach 5 ft., one target.
Hit: 14 (2d8 + 4) bludgeoning damage.

Disruptive Pulse (Recharge 5-6).
The Sentinel releases a pulse of arcane-disruptive energy in a 20-foot radius. Each creature in this area must succeed on a DC 15 Constitution saving throw or be unable to cast spells until the end of its next turn. Concentration spells end automatically if the caster fails this save.

Arcane Channeling Beam. (Recharge 6)
The Sentinel focuses absorbed magic into a destructive beam. A 60-foot line that is 5 feet wide blasts outward. Each creature in the line must make a DC 15 Dexterity saving throw, taking 27 (6d8) force damage on a failed save, or half as much damage on a successful one.