Akara will grant you this quest upon completion of the Sisters' Burial Grounds. Akara will tell you of a Horadrim sage named Deckard Cain, whom she believes will be able to advise the Rogues on their present situation. Deckard Cain can be found in the town of Tristram; however, the journey is too far on foot, so you must travel by way of the Cairn Stones located somewhere in Stony Field.
Akara goes on to explain that the only way to activate the Cairn Stones is to touch each one in a specific order. The proper order can be found within the runes on the bark of the sacred Tree of Inifuss, which you must bring to Akara for translation.
To find the Tree of Inifuss, you must travel to the Dark Wood, accessible only through the Underground Passage in Stony Field. The Tree of Inifuss is typically located by itself, and is guarded by a Super Unique Gargantuan Beast known as Treehead Woodfist. Once you have taken the Scroll of Inifuss, return to Akara in the Rogue Encampment.
After Akara has translated the runes, return to Stony Field and locate the Cairn Stones, which are guarded by a Super Unique Carver named Rakanishu. Using the Scroll of Inifuss as a guide, touch each of the Cairn Stones in the correct order to open a portal directly to Tristram. Deckard Cain can be found near the well in the center of Tristram, guarded by several Champion monsters. It should also be noted that both Griswold and Wirt can be found here as well, however, neither are what they once used to be.
If you do not rescue Deckard Cain before continuing to Act II, it will be considered a failed quest until a new game has been made. In this case, Deckard Cain will tell you that he was rescued by the Rogues, and you will have to pay in order to have your items identified by him.
Quest Activation Dialog
Akara:"It is clear that we are facing an Evil difficult to comprehend, let alone combat. There is only one Horadrim Sage, schooled in the most arcane history and lore, who could help us... his name is Deckard Cain. You must travel to Tristram. I pray that he still lives."
NPC Quest Dialog
Akara:"Tristram is too far to journey by foot... Cain would likely be dead when you arrived. However, there is a magical portal that will take you there instantly. To open it, one must stand within the circle of Cairn Stones and touch them in a certain order. The proper order can be found in the runes written on the bark of the Tree of Inifuss. You must find the sacred Tree of Inifuss and bring back its bark. I will translate the runes to unlock the Stones' mystic pattern."
Charsi:"If you bring back the bark of Inifuss, Akara will tell you how to get to Tristram."
Gheed:"I would sooner micturate in a tankard of my own ale than journey to Tristram!"
Kashya:"The bark of Inifuss holds mystical runes. Akara can translate them... into our revenge!"
Warriv:"Months ago, I came across a few survivors from Tristram. They said that Cain had gone half-mad and could no longer distinguish fact from fantasy."
Early Return I
Akara:"How will you find Cain without going to Tristram? Finding the Tree of Inifuss is the first step on your journey."
Charsi:"Without the bark of Inifuss you can't find Cain."
Gheed:"Barking up the wrong tree, huh? You'll find it, just keep looking."
Kashya:"The Tree of Inifuss is hard to find, but you'll know it when you see it."
Warriv:"He who seeks that which cannot be found must look inside himself for further guidance... or look harder!"
Early Return II
Akara:"Ah, very good. I have translated the runes on this scroll. You must find the Cairn Stones and touch them in the order that I have written."
Charsi:"Get this to Akara. Only she can understand it."
Gheed:"Look, friend... I trade a lot of strange items, but I'm not going to start dealing in bark. Okay?"
Kashya:"With this scroll you may open a portal back to Tristram. Only Akara can decipher its logic."
Warriv:"This looks like gibberish to me. Akara may know what to make of it."
Early Return III
Akara:"If he still lives, Deckard Cain may be in grave peril! You must hurry to Tristram before all is lost!"
Charsi:"I have heard that Tristram is now in ruins! Without Cain, I fear for the ruin of all of us."
Gheed:"I'm told that Tristram now resembles a mead hall... after a Barbarian wedding! I will wait here for your most glorious return."
Kashya:"Deckard Cain has crucial knowledge about the Evils we face. You must find him!"
Warriv:"It is too dangerous to travel to Tristram. I won't be leaving here until the way is clear!"
Akara:"You have risked your life to rescue Cain. For that we thank you. We must seek his counsel immediately."
Cain:(In Tristram) "...I thank you, friend, for coming to my aid." (In Rogue Encampment) "As a token of my gratitude, I will identify items for you at no charge."
Charsi:"Akara wishes to reward you for your bravery in returning Deckard Cain."
Gheed:"Ah, Cain is here... another customer. I haven't been this pleased since a love-starved maiden let down a bit more than her hair."
Kashya:"Again, you amaze me, outlander. The Sisterhood is grateful to you for delivering Cain to us. I believe Akara has something to tell you."
Warriv:"Only a brave adventurer could return with Deckard Cain. Akara has a reward for your valor."
Cain:"Blessings on the Rogues! They finally rescued me from that cursed place!"
Cain:"Regrettably, I could do nothing to prevent the disaster which devastated Tristram. It would appear that our greatest fears have come to pass. Diablo, the Lord of Terror, has once again been set loose upon the world! As you know, some time ago Diablo was slain beneath Tristram. And when our hero emerged triumphant from the labyrinth beneath town, we held a grand celebration that lasted several days. Yet, as the weeks passed, our hero became increasingly aloof. He kept his distance from the rest of the townsfolk and seemed to lapse into a dark, brooding depression. I thought that perhaps his ordeal had been so disturbing that he simply could not put it out of his mind. The hero seemed more tormented every passing day. I remember he awoke many times - screaming in the night - always something about 'the East'. One day, he simply left. And shortly thereafter, Tristram was attacked by legions of foul demons. Many were slain, and the demons left me to die in that cursed cage. I believe now that Tristram's hero was that Dark Wanderer who passed this way before the Monastery fell. I fear even worse, my friend... I fear that Diablo has taken possession of the hero who sought to slay him. If true, Diablo will become more powerful than ever before. You must stop him or all will be lost."
Character Quest Dialog
Amazon:"These stones serve some magical purpose."
Assassin:"These stones hold an ancient power."
Barbarian:"These magic stones are ancient."
Druid:"Hm. Such stones are common back home."
Necromancer:"I sense many spirits about these stones."
Paladin:"Maybe Akara could dispel the mystery of these stones."
Sorceress:"These stones radiate powerful magic."
Tree of Inifuss
Amazon:"What a strange-looking tree."
Assassin:"How has this tree escaped corruption?"
Barbarian:"This tree is one-of-a-kind."
Druid:"This dead tree teems with energy."
Necromancer:"This tree shines with inner spirit."
Paladin:"This tree bristles with magic."
Sorceress:"This ancient tree has an aura of magic about it."
Amazon:"It's as if a great war were fought here."
Assassin:"Tristram, the first to fall to Diablo's wrath."
Barbarian:"The land here is dead and lifeless."
Druid:"Ah, yes, ruins - the fate of all cities."
Necromancer:"All that's left of proud Tristram are ghosts and ashes."
Paladin:"What a tragic end to Tristram."
Sorceress:"Tristram was no match for Diablo's fury."
Amazon:"Deckard Cain! Go to the Rogue camp without delay!"
Assassin:"Cain, go to the Rogue camp!"
Barbarian:"Deckard Cain, you've got to get out of here!"
Druid:"Deckard Cain! Leave this place!"
Necromancer:"Deckard Cain, if you value your life, leave here immediately."
Paladin:"Deckard Cain, leave quickly!"
Sorceress:"Deckard Cain! Get to the Rogue camp!"