The Second Lightsaber Battle within the Jedi Temple was a confrontation involving Darth Vader, the Sith Lord, and Ferus Olin, a former Padawan, utilizing lightsabers. This event took place inside the Jedi Temple situated on Coruscant.
Olin gained entry to the Temple by way of a breakfast room located on the roof. From there, he found a staircase connected to a ruined atrium at the base of the High Council Tower. He ascended to the Jedi Temple Map Room, where he accessed the data storage and unearthed proof of a collaboration between Darth Vader and Flame, the woman who was meant to be assisting Olin. After deleting the message Flame had intended for Vader, Olin returned to the atrium, where he encountered Vader.
The duel began with Olin holding his own in the fight. With the turbolifts not functioning, Olin was forced to fight on the stairs leading up to the High Council Chamber. Inside the once immaculate chamber, the two combatants fought amidst the debris of the destroyed chairs in the circular room. As Vader's cape was blown back by the wind, Olin used taunts to distract the Sith Lord, allowing the former Jedi to strike a blow to the cyborg's control panel. Darth Vader attempted to dislodge Olin from the chamber through the shattered windows by throwing blackened furniture, floor tiles, and conduits torn from the ceiling.
The Sith holocron that Olin was carrying in his tunic pocket urged him to defeat Vader and become Darth Sidious's new apprentice. However, as Olin was pinned against the wall after a stumble, he felt the presence of the light side of the Force, as if the Jedi Masters were present in the Chamber once more. Overwhelmed by the lingering goodness in the ruins, Olin jumped over Vader and plunged through a hole in the floor, falling several stories into the Map Room. He then raced down through the Tower, heading towards the Temple's power core, where the remaining energies were sufficient to destroy the holocron and its malevolent power.
Vader located Ferus in the Core, but before he could deliver the final strike, he rushed out of the Temple on the orders of his Master to oversee the destruction of the Jedi asteroid.