Barioth

• Ice Walk. The dragon can move across and climb icy surfaces without needing to make an ability check. Additionally, difficult terrain composed of ice or snow doesn't cost it extra moment.
• Ice Acrobat.The dragon has +6 to its dexterity modifier when it's on ice and further more can't be knocked prone.
• Legendary Resistance (3/Day). If the dragon fails a saving throw, it can choose to succeed instead.

• Multiattack. The dragon can use its Frightful Presence. It then makes three attacks: one with its claw and two with its tail.
• Claw. Melee Weapon Attack: +12 to hit, reach 5ft., one target. Hit: (2d6 + 6) slashing damage.
• Tail. Melee Weapon Attack: +12 to hit, reach 15 ft., one target. Hit: (2d10 + 10) bludgeoning damage and must make a dc 18 dex save or be knocked prone.
• Bite. Melee Weapon Attack: +12 to hit, reach 15 ft., one target. Hit: (2d6 + 8) piercing damage plus (3d8)cold damage.
• Frightful Presence. Each creature of the dragon's choice that is within 120 feet of the dragon and aware of it must succeed on a DC 16 Wisdom saving throw or become frightened for 1 minute. A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success. If a creature's saving throw is successful or the effect ends for it, the creature is immune to the dragon's Frightful Presence for the next 24 hours.
• Icicle Breath (Recharge 4). The dragon exhales an icy blast in a 30-foot circle under it or 20-foot cone in front of it. Each creature in that area must make a DC 20 Constitution saving throw, taking 67 (15d8) cold damage on a failed save, or half as much damage on a successful one. Additionally the creature has to make a DC20 dex save, on a failed save the creatures movement speed is halved, all attacks on it have advantage and it has disadvantage on str,dex and con saves until it can get out of the icicles/affected area(the area that is affected is the area that was hit by the breath weapon, it will stay affected for 2 turns or until it's burnt of removed by other means.) 

Barioth can take 3 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. Barioth regains spent legendary actions at the start of their turn.

• Detect(1 legendary action).The dragon makes a Wisdom (Perception) check.
• Bite Attack(1 legendary action).The dragon can use its bite attack.
• Wing Attack (Costs 2 Actions).The dragon beats its wings. Each creature within 20 ft. of the dragon must succeed on a DC 20 Dexterity saving throw or take 15 (2d6 + 8) bludgeoning damage and be knocked prone. The dragon can then fly up to half its flying speed.