Bazelgeuse

Legendary Resistance (3/Day). If Bazelgeuse fails a saving throw, it can choose to succeed instead.

Charge. If Bazelgeuse moves at least 20 feet straight toward a target and then hits it with a Head attack on the same turn, the target takes an extra 10 (2d10) Bludgeoning damage. If the target is a creature, it must succeed on a DC 21  Strength saving throw or be knocked prone. 

Explosive Entry. If Bazelgeuse uses his charge or his fire breath through an area with explosive scales they explode and any creature within a 5 foot radius must make a DC 19 Dexterity Saving Throw or take 8(2d8) Fire damage.(Roll each scale Individually)

Multiattack. Bazelgeuse can use its Frightful Presence. It then makes three attacks: one with its tail and two with its Head.

Head. Melee Weapon Attack: +13 to hit, reach 5 ft., one target. Hit: 17(2d10 + 7) Bludgeoning damage.

Tail. Melee Weapon Attack: +13 to hit, reach 10 ft., one target. Hit: 16 (2d8 + 7) bludgeoning damage.

Frightful Presence. Each creature of Bazelgeuse' choice that is within 120 feet of the dragon and aware of it must succeed on a DC 19 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.

Fire Breath (Recharge 5–6). Bazelgeuse exhales fire in a 30-foot cone. Each creature in that area must make a DC 19 Dexterity saving throw, taking  63(18d6) fire damage on a failed save, or half as much damage on a successful one.

Bazelgeuse 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. Bazelgeuse regains spent legendary actions at the start of its turn.

Detect. The dragon makes a Wisdom (Perception) check.

Explosive Scales . Bazelgeuse scatters scales in a 15 foot cube where he stands. The scales stay on the ground until destroyed. When a creature makes an attack onto an area with scales they explode and any creature within a 5 foot radius must make a DC 19 Dexterity Saving Throw or take 8(2d8) Fire damage.

Revving up (Costs 2 actions). Bazelgeuse can move his full speed without provoking opportunity attacks and makes his charge head attack.