Savage Bludgeon- If Vjörn rolls a 19 or higher on an attack roll the target must make a Constitution saving throw or be knocked prone for 1d4 turns

Multiattack. Vjörn make a charge and a Frost mace attack
Charge. All targets in a 30ft cube must make a Dexterity saving throw or be knocked prone and take 2d10 bludgeoning and 2d4 cold damage

Frost Mace. Melee Weapon Attack: +9 hit, reach 10 ft., 10ft line. Hit: (2d8 + 4) bludgeoning and 2d6 cold damage. 

Breath Attack. RangedWeapon Attack: +9 to hit, 30ft cone , Hit: # (3d8 + 8) Cold damage. Make a Con or Dex save or be restrained for 1d4 turns.

Chilling presence. Vjörn releases an intense frost around him. All hostile creatures with 5ft make a Constitution save or take 1d4 cold damage on a fail and none on a success