Ambusher displacer beast

Avoidance. If the displacer beast is subjected to an effect that allows it to make a saving throw to take only half damage, it instead takes no damage if it succeeds on the saving throw, and only half damage if it fails.

Innate Spellcasting.  It can cast invisibility or blur at will as its innate spell casting.

Displacement. The displacer beast projects a magical illusion that makes it appear to be standing near its actual location, causing attack rolls against it to have disadvantage. If it is hit by an attack, this trait is disrupted until the end of its next turn. This trait is also disrupted while the displacer beast is incapacitated or has a speed of 0.

Cat darkvision. The displacer beast can see in magical darkness.

Keen Hearing and Smell. The displacer beast has advantage on Wisdom (Perception) checks that rely on hearing or vision.

Multiattack. The displacer beast makes two attacks with its tentacles or two with its claws, it can replace one of the usage of claws with a spellcast.

Tentacle. Melee Weapon Attack: +7, reach 10 ft. Hit: 7(1d6+4) magical bludgeoning damageplus 3(1d6) magical piercing damage.

Claws Melee Weapon Attack: +7, reach 5 ft. Hit: 7(3d6+4) magical slashing damage.

Hide The displacer beast can take the hide action in dimlight or darkness.