Clockwork Wyvern

Afterburners. The wyvern can consume 1 charge as a bonus action, doubling its flying speed until the start of its next turn.

Fuel. Over the course of a long rest, the wyvern can regain charges by consuming high-quality charcoal. It regains 1d4+1 charges for each 1 gp of charcoal consumed to a maximum of 10.

If the wyvern drops to 0 charges, the wyvern falls prone and unconscious until it is recharged with at least 2 gp of charcoal.

Immutable form. The wyvern is immune to any spell or effect that would alter its form.

Magic Resistance. The wyvern has advantage on saving throws against spells and other magical effects.

Mechanical Claw. Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 5 (1d6 + 2) piercing damage. 

Dragonling Breath (Recharge 5-6). The wyvern consumes 3 charges and exhales fire in a 15-foot cone. Each creature in the area must make a DC 14 Dexterity saving throw, taking 17(5d6) fire damage on a failed save, or half as much damage on a success.

Reconstitute. The wyvern consumes 1 charge, regaining 2d6+3 hit points.