Cor Kalom sends you to Y'Berion only after you are admitted to the Brotherhood ("Cor Kalom sends me to Y'Berion, the spiritual leader of the Brotherhood").
Swamp Camp, Temple Square — Chapter 1: Spiritual leader of the Brotherhood; you are sent to meet him as part of becoming a novice
Swamp Camp, Temple Square — later in the story: Leads the Great Awakening invocation using the focus stone; the contact overwhelms him and he collapses, then lies unconscious while you race to save him
During the Great Awakening his contact with the Sleeper through the focus stone overwhelms him and he collapses unconscious; he later dies, and scattering his ashes is the task that raises you to templar.
Quests Y'Berion takes part in across Gothic 1 Remake.
Y'Berion can be found in the Swamp Camp (Guru).
You: You mentioned a reward.
Y'Berion: You're right, I did. Even if what you did for us cannot be rewarded with worldly goods.
Y'Berion: Perhaps not. Here, take this - it's a talisman that will protect you from fire.
Y'Berion: What - who are you? Who let you in? GUARDS!