"A Musician's Nostalgia" (1x37) Upon returning to Emon, Tiberius announced to the other members of Vox Machina that he was leaving, as the "path of Vox Machina and the path of Tiberius Stormwind haven't been aligned for some time." Specifically, he hadn't made progress on his quests or earned the respect of his family.

What episode does Orion leave?

There were initially eight cast member players; Orion Acaba left the show after episode 27 of campaign one.

Why did Tiberius leave Critical Role?

I'm Tiberius Stormwind…from Draconia…” Orion has released an official statement today on his Twitch channel. Orion left of his own accord, because he had many ambitions beside Critical Role, and worked out that he could not do Critical Role and pursue his other ambitions.