When and where you meet them (avoid some spoilers more easily!):

• Nyoka: ACT 1 - Not far from Astarion, near the sea
• Myron: ACT 1 - Emerald Grove
• Elder: ACT 1 - Before the blighted village, under the bridge
• Kyth: ACT 1 - Meeting with the githyankis
• Azrael: ACT 2 - At the very beginning (you meet Azra, to be more precise)
• Oblivion: ACT 1 - Goblins' camp, in a prison
• Infinite: ACT 2 - Moonrise Towers, prison again
• Neo: ACT 3 - End of his personal quest