Following my Strahd encounter ideas series.
I now present an idea that is easily usable after the PC’s have been having a conversation with Strahd, or even if they are fighting him and insulting him during the fight (I always encourage RPing during fights). Better yet if one of the characters has insulted or disrespected Strahd. Strahd is short tempered and not at all used to being insulted, but he will react calmly and respond with witty questions.
When the PC’s attack him openly or Strahd decides it is the moment to act. He will move around the battlefield in a way that isolates the character who insulted him the most. He just needs to isolate him 10 feet to cast wall of force in the form of a hemispherical dome, trapping himself and the character inside it. Isolated from the rest of his enemies, Strahd is now free to insult and rip apart the offending character. The wall can’t be dispelled, the only hope is to attack Strahd and make him lose his concentration.
This can be easily resolved as a battle, Strahd can humiliate and destroy his enemy in front of his/her friends. They can watch as Strahd bites or murders their ally in cold-blood. On the other hand this is a great RP opportunity, Strahd can charm his target and then make the rest of the party beg for his life, or make a deal with them only to break his word and kill the character anyway. It’s up to the DM to decide this. At the end, after the cold-blood kill, or the deal. Strahd turns into mist and flies away.