Black Frost

Endure (Once per Long Rest). When the Black Frost is reduced to 0 hit points but not killed outright, it can drop to 1 hit point instead.

Repel Darkness. When the Black Frost would take necrotic damage because of another creature's attack or spell, it can force that creature to make a DC 15 Wisdom saving throw. On a fail, the creature takes the necrotic damage Black Frost would have taken instead. On a success, the creature only takes half the amount of damage.

Multiattack. The Black Frost makes three Ice Dracostrike attacks or it makes two Mudoon attack.

Ice Dracostrike. Melee Weapon Attack: +8 to hit, reach 5 ft., 1 target. Hit: 7 (1d6 + 4) slashing damage plus 9 (2d8) cold damage.

Mudoon. Ranged Spell Attack: +7 to hit, reach 60 ft., 1 target. Hit: 16 (3d8 + 3) necrotic damage or 19 (3d12 + 3) necrotic damage if the target is missing any of its hit points.

Mabufula (Recharge 5-6). Black Frost makes a ranged spell attack (+7 to hit) against all creatures of his choice within 30 feet of him. On a hit, the attack deals 10 (2d6 + 3) cold damage.

Tarunda (3/Day). The Black Frost chooses a creature it can see within 30 feet of it, the target must make a DC 15 Charisma saving throw. On a fail, the creature subtracts 1d4 from all their damage rolls for their next 3 truns.