Den of Evil
The Den of Evil is the first quest received from the exiled Rogues, given to you very shortly after beginning the game from the priestess Akara. The Den is located beyond the camp palisades in the Blood Moor, the first region with hostile enemies. The weakest of these enemies are the demons called Fallen, next strongest are the Quill Rats, and Zombies. All enemies in this area are comparatively weak, and can be killed with one or two hits from your starting weapon. To reach the Den, follow the dirt path through the Blood Moor until you reach a cave opening; this is the Den of Evil.
The objective of this mission is to slay all enemies within the Den. The enemies inside are identical to what you confronted in the Blood Moor, except for a couple important additions. The first is your introduction to the Fallen Shaman, a demon much like the other Fallen except that they attack with a fire bolt which does more damage, and can revive Fallen that you have killed. You can find these enemies in packs with other Fallen. The easiest way to deal with Shamans are to kill them before the other Fallen, so that they don't get the opportunity to bring every Fallen you kill back to life. The second new enemy is Gargantuan Beast (a.k.a. Wendigo), a towering brute can take more hits than other monsters and deals more melee damage. Eventually, you will encounter your first Super Unique monster, a zombie named Corpsefire who has more health and deals more damage than other zombies. It will take a few extra hits to kill Corpsefire, but the items he drops are potentially more valuable than other monsters.
When the last monsters have been cleared from the Den, the red glow will disappear and light will flood the cave. When you return to the Rogue Encampment, speak to Akara and she will reward you with an extra skill point.
Sisters' Burial Grounds
Your second quest from the Rogues comes from Akara's second-in-command Kashya, and becomes available immediately after completing the Den of Evil quest. She tells you of one of the Rogues' finest captains, named Blood Raven, who despite her valor and dedication to the Rogues' cause had been corrupted by the demoness Andariel. Your task is to travel to the Sisters' Burial Grounds and kill Blood Raven to prevent her from raising an undead army.
Your first objective is to traverse the Blood Moor to the second region in Act I, called the Cold Plains. Simply follow the dirt path through the Blood Moor, killing or ignoring enemies at your leisure depending on if you gain experience. You will know you've found the end of the moor when you meet the Rogue archer Flavie. She will warn you to be careful in the next area, which you should be aware of throughout the game. The enemies in each successive area are considerably stronger, and you will find out for yourself in the Cold Plains.
Upon entering the Cold Plains, follow the dirt path a little ways until you see the waypoint off to the side. Waypoints make travel within the game much more convenient by enabling instantaneous teleportation, second only to Scrolls of Town Portal. The enemies in the Cold Plains include the Fallen and Fallen Shamans, Gargantuan Beasts, and the Corrupted Rogues. The Rogues are fast warriors that will often catch you off guard, and they travel in packs. Some will even strike at you within melee range while others shoot at you from across the screen.
To find the Burial Grounds, follow the dirt path through the Cold Plains, however there are forks in the road, one way will take you where you want to go, the other will lead you to the Stony Field, which you should remember for later. The Burial Grounds itself is relatively small, Blood Raven herself is waiting within the fenced area. Follow along the outside of the fence to find gaps to walk through, killing the Skeletons and Skeleton Archers along the way. When Blood Raven is within your view in the center of the cemetery she will begin shooting fire arrows at you that do considerable damage. In addition to fire arrow, Blood Raven can summon zombie-like creatures called Hungry Dead to attack you. The best strategy for taking her down is to ignore the Hungry Dead and focus your attacks solely on Blood Raven. She will run around the cemetery at a fast pace but will usually attack comparatively slowly, as she will tend to waste time raising more zombies, which gives you opportunities to hit her instead. Blood Raven is a Super Unique monster, so she has considerable health, but can drop valuable items.
When Blood Raven dies, bolts of lightning will fill the screen and her spirit will evaporate. All Hungry Dead that are in the graveyard will automatically die. When you return to the Rogue Encampment, Kashya will recognize your victory by supplying you with a Rogue Mercenary to accompany you on your travels.
The Search for Cain
The third quest from the Rogues is given to you by Akara after killing Blood Raven. She explains to you the magnitude of evil which you are facing in your journey and suggests that a Horadric Mage, named Deckard Cain would prove to be a powerful ally. Akara believes that Cain resides in Tristram, and that the quickest way to the city is through the use of the Cairn Stones in the Stony Field.
Akara will send you off to the Dark Wood to find the Tree of Inifuss which holds the answer to the Cairn Stones. First off, head to the Stony Field, you should find the Cairn Stones there but do not approach it yet, ignore it and continue to find a cave called The Underground Passage Level 1. You will find considerably stronger monsters in there particularly more corrupted rogues. Once you pass through the area, you'll find yourself in the Dark Wood.
The Dark Wood
The Tree of Inifuss is fairly hard to find considering Dark Wood is a pretty big area. You'll know when you find it if you bump into a unique monster called Treehead Woodfist (a Wendigo) followed by two of his minions, kill them if you can and speak to the tree in order for it to drop the scroll. Once you obtained the scroll, you can either use a town return scroll or the Waypoint here to return to the Rogue Encampment. Speak to Akara there to receive further instructions.
Tristram
Akara will tell you to read the runes on the scroll. Do so by right clicking on the scroll and you'll realise numbers would appear on the stones in the scroll. If you've seen the Cairn Stones in the Stony Field, go there now. If not then explore around untl you find stone like structures on your map. Be careful when approaching the Cairn Stones because another Super Unique Monster will fight you. It is Rakanishu which is a lightning enchanted carver, it's shock web attack is not laughable as it hits fairly hard if you do not have high resistance. Once you defeat Rakanishu, talk to the stones by clicking on them in a specific order as shown on the scroll and a red portal would appear taking you to Tristram.
Once you enter Tristram, you'll realise that the whole town has been obliterated and is currently being occupied by undead. Stay away from the dead cows in the area unless you don't mind taking damage. Deckard Cain is right in the middle of town, simply talk to the cage to free him but be mindful of the monsters around you namely the three super unique monsters. Remember Diablo I? Well you might find ome familiar faces here, it seems that the blacksmith Griswold has succumbed to the evil much like Blood Raven had. Well to make things short, Griswold has enhanced strength and has a ridiculously high stamina to boot. Take him down for good item drops and to prevent him interfering with your mission, it may take a while however. Once you've taken down everything here, you might want to find Wirt who apparently is killed in the attack. Talk to the corpse to receive lots of gold and his legs which acts as an ordinary club. Keep this item until the end of the game to find an interesting little secret.
The Forgotten Tower
Unlike the oter quests in Act I, this is triggered by an NPC outside the Rogue Encampment and it is an optional quest. To trigger this quest, find the Mouldy Tome in the Stony Field to learn about "the countess who once bathed in the blood of a hundred virgins was buried alive in a tower". Interesting, now head to the Black Marsh to find the Dark Tower, don't know how to get there? Well it's accessible from Dark Wood if you've done the "Seach for Cain" quest. Whilst you're at the Black Marsh, it is recommend to look for the waypoint as well which would prove useful. Once you find the tower (not much of tower since it's collapsed) head into the cellars, your destination is the 5th floor of the cellar. Don't worry too much about navigation since the cellars are relatively small, the only thing you should be worried about here is the Super Unique monster on every floor ranging from undead wraiths to zombies. Once you arrive on the 5th floor, explore around the area and open every chest to obtain mounds of gold, the Countess is located in the back room and oddly, she's a fire enchaned corrupted rogue. Furthermore she is surrounded by her fellow rogues to back her up. Pull out the minor rogues out of the room slowly and kill them before facing the countess. The countess shouldn't be too hard so the fight would be relatively quick. The quest ends as soon as you defeat the Countess.