strength contest. any magic user facing demon knight Heinrich takes an extra 1d6 of dmg when they get hit with any attack

Demonic pursuit.Once this monster takes sight of you, it will pursuit you until its death. if he is not killed in 6 rounds, he disappears for 30 rounds then reappears next to the adventurer(s) after 30 the 30 rounds are up. roll 1d20 to see how much health it gets back on the next encounter.

pitch black stab. Melee Weapon Attack: +14 to hit, reach 5 ft., 1 target. Hit: 1 (1d12 + 5) [peircing] damage. 

sword sweep. MeleeWeapon Attack: +12 to hit, range 10 ft all around heinrich, any target in range. Hit:  1(1d10 + 4) [slashing] damage.

dark zone.  15+ to hit Heinrich makes everything  in a 50 by 50 ft radius pitch black for 4 rounds, you must make a perception check of 12 or higher each round to act against him.

Anxious end. You are frightened for 15 rounds after Heinrich disappears as you wait in anticipation for his next return.

Legendary actions can only be used when Heinrich goes below 45hp. after this he can use as many legendary actions that he can per round. He will always use last resort first in this condition
                        

Last resort (Costs 1 Action and can only be used once). Heinrich takes his helmet off permanently, revealing a shadow like mist. he does not disappear anymore and now has 2 actions per round.

assassins mist(cost 1 action) Heinrich opens a small portal from his mist and shoots sharp pitch black projectiles at the person with the lowest hp. roll 5d4 for dmg. If 2 or more have the same hp, he targets the person with the lowest armor class.

mist cloak(cost 1 action)  heinrich cloaks himself in his dark mist. Heinrich gains +5 to his armor class, this only stacks twice

mist restraint(cost 1 action) Heinrich turns his mist into 2 steaks, pinning you to the ground for 2d10 dmg, you are restrained for your next turn.