Reaper of Souls - Achievement Guide - Tales of the Once-ler

0:00 - The Horadrim - begin at Act 5.2 (Souls of the Dead); speak with Lorath Nahr.

Start at the "Talk to the Mystic" quest-checkpoint under Act 5.2 (Souls of the Dead); two conversations will be availabe:
0:20 - Diablo Slayer
0:42 - Lorath's History

1:12 - Cain - begin at Act 5.3 (The Harbinger); speak with Lorath Nahr.
1:36 - Destroying the Soulstone - immediately following the conversation "Cain," speak with Tyrael to advance the quest, watch/skip the cutscene, then this conversation will be available.
2:19 - Pandemonium Fortress - begin at Act 5.6 (The Battlefields of Eternity); speak with Lorath Nahr.
2:38 - Rebuilding - start at the "Siege Runes" quest-checkpoint under Act 5.6 (The Battlefields of Eternity); speak with Lorath Nahr.
3:05 - The New Horadrim - begin at Act 5.7 (Breaching the Fortress); speak with Lorath Nahr.
3:24 - Pandemonium - begin at Act 5.8 (Angel of Death); waypoint to Pandemonium Fortress Level 1, speak with Tyrael to advance the quest, then return to the Enclave and speak with Lorath Nahr.