Animated Trap

Antimagic Susceptibility. The trap is incapacitated while in the area of an antimagic field. If targeted by dispel magic, the trap must succeed on a Constitution saving throw against the caster's spell save DC or fall unconscious for 1 minute.

Assassinate. During its first turn, the trap has advantage on attack rolls against any creature that hasn't taken a turn. Any hit the trap scores against a surprised creature is a critical hit.

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

Sneak Attack (1/Turn). The trap deals an extra 7 (2d6) damage when it hits a target with a weapon attack and has advantage on the attack roll, or when the target is within 5 feet of an ally of the trap that isn't incapacitated and the trap doesn't have disadvantage on the attack roll.

Thieves' Tools Susceptibility. If targeted by thieves' tools, The trap makes a Constitution saving throw contested by the opposing creature's thieves' tools check. If the trap wins it can make a bite attack as a reaction against the opposing creature. If the trap loses it is stunned until the end of its next turn.
Additionally if the trap loses by 5 or more the opposing creature realizes the true nature of the trap.

Multiattack. The trap makes three attacks.

Bite. Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 14 (2d8 + 5) piercing damage and the target is grappled (escape DC 16).

Crush. Melee Weapon Attack: +8 to hit, reach 5 ft., one creature grappled by the trap. Hit: 16 (2d10 + 5) piercing damage.