Shapechanger. Zafrios can use its action to polymorph into a drake-humanoid hybrid or into a drake, or back into its true form, which is humanoid. Its statistics, other than its AC and Size, are the same in each form. Any equipment it is wearing or carrying isn't transformed. It reverts to its true form if it dies.
In it's full drake form Zafrios became Large size.

Keen Hearing and Smell. Zafrios has advantage on Wisdom (Perception) checks that rely on hearing or smell.

Multiattack. Zafrios makes two attacks: two with its claws (Hybrid form) or one with its bite and one with its claws (Drake form).

Thunder Punch (Humanoid Form Only). Melee Weapon Attack: +9 to hit, reach 5 ft., one target. Hit: 8 (1d6 + 5) bludgeoning damage plus 7 (2d6) thunder damage.

Bite (Drake or Hybrid Form Only). Melee Weapon Attack: +9 to hit, reach 5 ft., one target. Hit: 10 (1d10 + 5) piercing damage, or 16 (2d10 + 5) piercing damage if used in Drake Form.

Claws. (Drake or Hybrid Form Only). Melee Weapon Attack: +9 to hit, reach 5 ft., one target. Hit: 12 (2d6 + 5) slashing damage.

Tail. (Drake Form Only). Melee Weapon Attack: +9 to hit, reach 10 ft., one target. Hit: 15 (3d6 + 5) bludgeoning damage.

Lightning Explosion (Recharge 5–6). Zafrios explode a lightning in his mouth, each creature Zafrios can see that is within 25ft. takes 20 (5d6) lightning damage and must make a DC 17 Constitution saving throw, taking 29 (6d8) thunder damage on a failed save, or half as much damage on a successful one.

Zafrios can take 2 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. Zafrios regains spent legendary actions at the start of its turn.

Detect. Zafrios makes a Wisdom (Perception) check.

Tail Attack. Zafrios makes a tail attack.

Thunder Punch Attack. Zafrios makes a thunder punch attack.