Enrage. When the Serenas' HP drops below 53 (3/4) it immediately becomes enraged. When the hoarfrost Serenas' HP drops below 18 (1/4) its enrage ends, as it becomes too physically weak to maintain. While Enraged, its melee attacks deal an additional 2 (1d4) cold damage
Flyby. The Serenas does not provoke an opportunity attack when it flies out of an enemy's reach.
Multiattack. The Hoarfrost Serenas makes two attacks: one with its beak and one with its talons.
Beak. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 6 (1d6 + 3) piercing damage.
Talons. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 12 (2d6 + 3) slashing damage, and the target is grappled (escape DC 13). Until this grapple ends, the target is restrained, and the Hoarfrost Serenas can't use its talons on another target.