Here's what happened:
* Obi-Wan Kenobi: He arrived on the Death Star with Luke Skywalker and Han Solo to rescue Princess Leia.
* Darth Vader: As the Imperial enforcer of the Death Star, Vader was alerted to their presence.
* The Duel: Obi-Wan and Vader engaged in a lightsaber duel in the Death Star's trash compactor. This was a climactic fight, marking the first time the two former friends clashed in a major way since Obi-Wan left Anakin to become Darth Vader.
The Outcome:
* Obi-Wan seemingly died in the duel, but he actually became one with the Force.
* Vader emerged victorious, but he was also deeply affected by his encounter with his former Master.
It's important to remember that while the confrontation was physical, it was also symbolic of their emotional and spiritual connection. It represented the ultimate clash of good and evil, Jedi and Sith, and their final confrontation before the ultimate battle between Luke and Vader.
It's not accurate to say they "formed" anything, but their duel was pivotal for the story and for their individual journeys.