Lavaice Walk. The drake can move across and climb icy, earthen, and lightly-lava-covered surfaces without needing to make an ability check. Additionally, difficult terrain composed of ice, snow doesn't cost it extra movement.

Lesser Legendary Resistance (1/Day). If the drake fails a saving throw, it can choose to reroll it with advantage.   

Multiattack. The drake makes two melee attacks.

Bite. Melee Weapon Attack: +7 to hit, reach 5 ft., 1 target. Hit: 10 (2d6+3) piercing damage plus 3 (1d6) fire or lightning damage (drake's choice).

Horns. Melee Weapon Attack: +6 to hit, reach 5 ft., 1 target. Hit: 10 (2d6+3) piercing damage plus 1 bludgeoning damage.

Claw. Melee Weapon Attack: +5 to hit, reach 5 ft., 1 target. Hit: 7 (2d4+3) slashing damage. 

Tail. Melee Weapon Attack: +5 to hit, reach 10 ft., 1 target. Hit: 7 (2d4+3) bludgeoning damage plus 6 (1d6+3) piercing damage. 

Bolt Spit. RangedWeapon Attack: +5 to hit, range 35/260 ft., 1 target. Hit: 9 (3d4+1) lightning damage.

Giant Crack (Recharge 3-6). The drake channels primal, warring energy through its body to cause a 10 foot long, 10 foot wide glowing orange fiery crack to appear within 10 ft of a Medium or smaller creature. That creature must make a DC 14 Dexterity saving throw or take 7 (2d6) fire damage and be knocked prone and grappled by being trapped in the crack (escape DC 15), or half as much damage and just be knocked prone 15 feet away from the crack on a success. While grappled in this way, the creature takes 2 fire damage at the start of each of its turns for 1 round, after which the crack disperses and the grappled creature, if it has not escaped yet, falls prone in a space within 10 ft of the crack.

Thunderbolt Laser (Recharge 6). The drake unleashes a flaming electric laser blast from its chest in a 20 ft long, 10 ft wide line. Each creature in that area must make a DC 14 Dexterity saving throw, taking 13 (3d6) fire damage and 13 (3d6) lightning damage on a failed save, or a third as much on a success.