Bio-Arcane Sentinel

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

Magic Resistance. The sentinel has advantage on saving throws against spells and other magical effects.

Rune Scan (Awakening Only). When the sentinel first activates, it emits a pulse of arcane energy. Each creature within 20 feet must make a DC 15 Wisdom saving throw. On a failure, the sentinel briefly reads that creature's surface thoughts — the DM may reveal a one-sentence summary of what that creature is currently thinking or intending. This trait activates once per awakening and is purely informational; it does not impose a condition.

Assess Threat. A creature that can see the sentinel's runes can make a DC 16 Intelligence (Arcana) check to determine whether the sentinel is in defensive mode or hostile mode, and what conditions might satisfy it. Alternatively, a creature can make a DC 14 Charisma (Persuasion) check to convince it of non-threatening intent, shifting it to guarded-neutral status. On a guarded-neutral result, the sentinel ceases attacking and may answer up to three questions or indicate a safe passage, at the DM's discretion.

Construct Nature. The sentinel doesn't require air, food, drink, or sleep.

Multiattack. The sentinel makes two rune bolt attacks, or one rune bolt attack and uses Binding Field.

Rune Bolt. Ranged Spell Attack: +7 to hit, range 60/120 ft., one target. Hit: 18 (4d6 + 4) force damage, and the target must succeed on a DC 15 Constitution saving throw or have disadvantage on its next attack roll as the runes momentarily disrupt its concentration.

Slam. Melee Weapon Attack: +9 to hit, reach 5 ft., one target. Hit: 19 (4d6 + 5) bludgeoning damage. The target must succeed on a DC 17 Strength saving throw or be pushed 10 feet and knocked prone.

Binding Field (Recharge 4–6). The sentinel projects a field of arcane force in a 15-foot cube originating from itself. Each creature in the area must make a DC 15 Strength saving throw or be restrained until the end of its next turn. Creatures that succeed cannot be affected by Binding Field again for 24 hours.

Rune Flare (Recharge 5–6). The sigils on the sentinel's chest erupt in a 20-foot-radius burst of arcane light. Each creature in range must make a DC 15 Constitution saving throw, taking 28 (8d6) radiant damage on a failure and being blinded until the end of its next turn, or half damage and not blinded on a success. Constructs and undead have disadvantage on this saving throw.

Arcane Rebuke. When the sentinel is hit by a spell attack, it can use its reaction to absorb part of the energy. It takes half damage from the triggering attack and gains 10 temporary hit points.