shamelessly stealing the king black dragon from runescape

>adult black dragon
>but with 2 additional heads
>loses 1 head at 100 damage taken, loses its second head at 150 damage taken
>each head attacks a different target from the other heads and acts at initiative -5 and -7

>left head makes 1 rend attack and then uses an ice attack
>right head makes 1 rend attack and then uses a shock attack
>main head uses adult black dragon stats, but can choose between poison or fire breathe

>shock attack: +11 to hit, 2d8 lightning damage, if it hits the target cant take reactions for one turn, 50ft range
>ice attack: +11 to hit, 2d8 cold damage, if it hits the target its speed is reduced by 10ft for one turn