Argenteryx

Keen Sight and Smell. The argenteryx has advantage on Wisdom (Perception) checks that rely on sight or smell.

Bad Flier. The argenteryx falls at the end of a turn if it's airborne and the only thing
holding it aloft is its flying speed.

Divebomb. If the argenteryx moves at least 20 feet toward a target and hits the target with a melee attack, the target takes an additional 6 (1d12) damage, or 7 (2d6) damage if the argenteryx moved at least 20 feet straight downward.

Multiattack (Only usable while at Half-Hit Points or lower). The argenteryx makes three melee attacks, and if all attacks hit, the argenteryx regains 1d10 hit points, gains advantage on saving throws against any conditions affecting it for 1 minute, and the argenteryx's number in the initiative increases by 1 for 1 minute as well.

Beak. Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 4 (1d4 + 2) piercing damage.

Talons. Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 6 (1d8 + 2) slashing damage.

Debilitating Devise. In response to the Argenteryx making the Ready action on its turn on the first round of it being in combat, each hostile creature within 5 feet of the argenteryx must succeed on a DC 15 Wisdom saving throw or have a -3 bonus to damage dealt by the creature's attacks