Flyby.

The peryton doesn't provoke opportunity attacks when it flies out of an enemy's reach.

Keen Sight and Smell.

The peryton has advantage on Wisdom (Perception) checks that rely on sight or smell.

Legendary Resistance (3/Day).

If the peryton fails a saving throw, it can choose to succeed instead.

Actions

Multiattack.

The peryton makes two attacks: one with its gore and one with its talons.

Gore.

Melee Weapon Attack: +9 to hit, reach 5 ft., one target. Hit: 12 (2d6 + 5) piercing damage.

Talons.

Melee Weapon Attack: +9 to hit, reach 5 ft., one target. Hit: 16 (2d10 + 5) slashing damage.

Warp Shadow.

The peryton chooses up to three creatures within 60 feet of it that it can see. Each creature must succeed on a DC 14 Wisdom saving throw or become cursed. While cursed, whenever the creature makes an attack roll, an ability check, or a saving throw, it must roll a d4 and subtract that number from the roll. A cursed creature can repeat this saving throw at the end of each of its turns, ending the effect on itself with a success. A creature that succeeds on this saving throw is immune to this peryton's Warp Shadow for 24 hours.

Legendary Actions

The monstrous peryton can take 3 legendary actions, choosing from the options below. Only one legendary action can be used at a time and only at the end of another creature's turn. The monstrous peryton regains spent legendary actions at the start of its turn.

Detect. The peryton makes a Wisdom (Perception) check.
Talons Attack. The peryton makes one attack with its talons.
Dive Attack (Costs 2 Actions). The peryton moves up to its speed toward one target of its choosing. It then makes a gore attack that deals an extra 9 (2d8) piercing damage on a hit.

Monstrous Peryton