All Ears

Act 1

#	NPC	Dialog	Conditions
1	Dying Exile		First dialog in the game
2	Nessa	Introduction	Entering town for the first time
3	Bestel	Introduction	Entering town for the first time
4		Medicine Chest
5		Drowned Dead
6	Tarkleigh	Introduction	Entering town for the first time
7		Lioneyes Watch
8		Drownded Dead
9	Nessa	Bestel	After first talk to Bestel
10	Tarkleigh	Bestel
11	Bestel	Nessa	After first talk to Nessa
12	Tarkleigh	Nessa
13	Nessa	Tarkleigh	After first talk to Tarkleigh
14	Bestel	Tarkleigh
15	Tarkleigh	Scavangers	After first enter to Tidal Island
16	Nessa	Rhoas	After first enter to Mud Flats
17	Tarkleigh	Rhoas
18	Bestel	Undead Rhoas	After killing the unique rhoa in Mud Flats [perhaps only on Cruel and Mercilles]
19	Tarkleigh	Glyph Wall	After walk near the glyph wall, before putting glyphs in it
20	Nessa	Surviving Wreaclast	After getting quest "The way forward"
21	Bestel	Surviving Wreaclast
22	Nessa	Brutus	After getting quest "The Caged Brute"
23	Bestel	Brutus
24	Bestel	Marceus Lioneye	After reading Shavronne's Journal in The Upper Prison in The Warden's Quarters
25	Nessa	Brutus	After killing Brutus
26	Bestel	Blocked road	After meeting Piety in front of Prisoner's Gate
27		Shavronne
28	Nessa	Ship Graveyard	After enter to Ship Graveyard
29	Bestel	Merveil	After getting quest "The Siren's Cadence"
30	Tarkleigh	Merveil
31	Fairgraves	The Allflame	First talking to Fairgraves
32		Merveil
33		Merveil's Necklace
34	Bestel	Captain Fairgraves	Talk to Bestel 'right after talking to Fairgraves
35	Fairgraves	The Real Fairgraves	Talk to Fairgraves after talking to Bestel (Captain Fairgraves)
36	Nessa	Merveil	After killing Merveil
37	Bestel	Merveil
38	Tarkleigh	Merveil
39	Nessa	Reopened passage	After reopening the passage in Western Forest
40	Bestel	Reopened passage
41	Tarkleigh	Inspirational Poem

Act 2

#	NPC	Dialog	Conditions
1	Eramir	Introduction	Entering town for the first time
2		The Azmeri
3		Blocked Passage
4	Yeena	Introduction	Entering town for the first time
5		Blood Apes
6	Silk	Introduction	Entering town for the first time
7	Greust	Introduction	Entering town for the first time
8		Blood Apes
9	Yeena	Eramir	After first talk to Eramir
10	Silk	Eramir
11	Greust	Eramir
12	Eramir	Yeena	After first talk to Yeena
13	Silk	Yeena
14	Greust	Yeena
15	Eramir	Silk	After first talk to Silk
16	Yeena	Silk
17	Greust	Silk
15	Eramir	Greust	After first talk to Greust
16	Yeena	Greust
17	Silk	Greust
18	Silk	The Great White Beast	After getting quest "The Great White Beast"
19	Greust	Elementals	After enter to Old Fields
20	Yeena	Elementals
21	Silk	The Great White Beast	After killing The Great White Beast
22	Greust	Chamber of Sins	After killing blackguard Captain Arteri in The Western Forest
23	Eramir	Blackguards
24	Silk	Blackguards
25	Silk	Reopened passage	After reopen passage in The Western Forest
26	Eramir	Ancient Gateway	After clicking on the tree roots in The River Ways without poisoning it
27	Yeena	Chamber of Sins	After enter to Chamber of Sins
28	Eramir	Helena	After rescuing Helena from Fidelitis, the Mourning
29	Yeena	Helena
30	Silk	Helena
31	Greust	Helena
32	Helena	Fidelitis	First Talk to Helena in town
33		Elementals
34		Prisenor's Gate
35		Ancient Gateway
35	The Baleful Gem	Talk to Helena with The Baleful Gem in inventory
35	npc	dlg	text
35	npc	dlg	text
35	npc	dlg	text

The appearance of the dialogues during a quest "Deal with the Bandits" described in one of the possible sequences. It is important that at every level of difficulty you have helped various bandits or noone. More importantly, it is a sequence of killing other two bandits when you help the third. And yes, you must buy Book of Reform to get this Achievement.