Amphibious. The dragon can breathe air and water.

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

Soal steal. Any time someone in your party falls to 0 health, that player must make a survival saving throw or instantly die and the bone dragon will instantly absorb your, it can be released if the dragon uses up all the souls in the breath weapon or when the dragon dies your soul will be released and you will be returned to your previous position (only works if in dragon's lair)

Brittle Bones. the dragon must take one action to rebuild itself if knocked prone

Undead. this creature does not need air, food, drink, or sleep.

Multiattack. The dragon can use its Frightful Presence. It then makes three attacks: one with its bite and two with its claws.

Bite. Melee Weapon Attack: +11 to hit, reach 10 ft., one target. Hit: 17 (2d10 + 6) piercing damage plus 4 (1d8) acid damage.

Claw. Melee Weapon Attack: +11 to hit, reach 5 ft., one target. Hit: 13 (2d6 + 6) slashing damage.

Tail. Melee Weapon Attack: +11 to hit, reach 15 ft., one target. Hit: 15 (2d8 + 6) bludgeoning 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.

Soal Wind Breath (Recharge 6). The dragon exhales 5 soals compacted into an invisible line (for any character with a 0 or negitive peception) that deals 10(5d4) necrotic damage per enemy and heals the dragon for half of its total damage (rounded down), after the attack you must roll a d6 and what you get you must subtract from your total soals of 11(1d20) if the dragon has less than 5 soals when it uses this attack, only use a d4 per soal, this attack cannot be used if the dragon has no soals.

Curse. Any time you physically hit the dragon or use necrotic magic against the bone dragon, the bone dragon has the choice the curse one player, giving that player disadvantage on all attacks against the dragon, the players character healing spells and potions are halved for themselves and anyone they heal when cursed, and if the players character drops to 0 hit points, their soul is taken without any saving throw occuring, this curse is removed from the player if the dragon decides to use it on another player.