At the end of episode 5, Jayce escapes from whatever it was that captured him, Ekko, and Heimerdinger at the end of episode 3. Dishevelled and clearly altered by his experience during the time between episodes 3 and 4, Jayce wastes no time in killing Salo (ostensibly cured by Viktor), before heading to Viktor's compound in episode 6.
Clearly, something is up with Piltover's heroic man of progress. He seems scarred by whatever he's seen, telling Salo he can't let him leave the Hexgate chamber he finds him in before smashing him with his hammer. When he arrives at the compound, he's clearly pained by multiple visions, and while he's able to fight those off, he immediately heads towards Viktor, appearing to kill him with a massive blast from his augmented weapon.
