Special Trait Names. 

Magic resistance: The abyssal drake has advantage on saving throws against spells and other magical effects.

Flyby: The abyssal drake doesn't provoke opportunity attacks when it flies out of an enemy's reach. 

Awakened mind: Unlike its closely related cousin, the wyvern, the abyssal drake is intelligent enough for conversation. Inherently born with the gift to speak and understand the abyssal and draconic languages, it may speak with those it encounters.

Spellcasting. The [Abyssal Drake] is a 1st-level spellcaster. Its spellcasting ability is [charisma] (spell save DC 15, +2 to hit with spell attacks). The [Abyssal Drake] has following [sorcerer] spells prepared:
Cantrips (at will): [green flame blade], [Fire bolt] 
1st level (2 spell slots): [Ray of sickness], [burning hands] 

Multi-attack. The drake makes three attacks: one with its bite, one with its claw, and one with its stinger. It can make a second claw attack in place of its stinger. If both claw attacks hit, the abyssal drake rends through flesh dealing an additional 2d6 damage.

Action Melee Attack. Claw Attack: +2 to hit, reach 5 ft., 1 target. Hit: 14 (1d6 + 3) [slashing] damage. 

Bite Attack: +2 to hit, reach 5 ft., 1 target. Hit: 16 (1d10 + 3) [piercing] damage and con save against poison. 

Body slam Attack: +3 to hit, reach 15 ft., 1 target. Hit: 15(1d12 + 2) [bludgeoning] damage. 

Action Ranged Attack. Spike launch Attack: +3 to hit, range 10/40 ft., 1 target. Hit:  17(1d8 + 3) [piercing] damage and con save against poison: 16

Breath weapon attack: +2 to hit, range 60 foot long cone of necrotic fire, multiple targets. Hit: 15(1d8 fire damage and 1d8 necrotic damage +4 ) dex save: 17

Cantrips

Reaction Name. Opportunity attack

Isn't legendary

Isn't mythic