Step onto the New Tristram Waypoint and select the Old Ruins location.
Allow Leah to open the gate, and lead the way through it and northeast along Old Tristram Road.
Blast through the few Risen that appear, and listen to Leah talk about her mother, Adria.
Arrive at and enter Adria’s Hut.
Follow Leah through the entrance to the Hidden Cellar.
Move to the central room in the Cellar, where a number of Risen attack, along with the former Captain of the Guard, Captain Daltyn, now in undead form.
Captain Daltyn is merely an enhanced Risen, with a bit of a stranger punch, but just as slow-moving. Focus attacks on him while Leah deals with the other Risen.
Search the cauldron in the center of the room.
Speak to Leah, who will give you the key to the Cathedral, and stay behind to learn more her mother.
Exit the Hidden Cellar and fend off another Risen attack, which opens up the path to the north.
Continue northward along Old Tristram Road toward the Cathedral, smashing through a few more Risen and Walking Corpses.
Search the bodies of any dead militia you find along the way.
Arrive at the Cathedral, and search around outside for any hidden loot.
Enter the Cathedral, and move up to the glowing blue pit where the fallen star landed.
Click the pit to jump down and begin the trek through the Cathedral in search of Deckard Cain.
Grotesques are large, bloated, Buddha-turned-undead creatures with two dangers: a sudden spike growth from their bodies for a melee attack, and an AoE explosion upon their death which releases 3 Corpse Worms that continue to seek you out.
Carrion Bats attack swarming in and stinging, then flying away to safety, and returning for another attack.
Molten Carrion Bats attack the same as above, but have Fire attack and resistance, and explode when they die. Beware.
Pay close attention to the environment here, as you’ll find many traps that may be used against creatures, such as falling chandeliers and loosely propped-up sections of wall. Use them to your advantage.
Search through this level of the Cathedral to find Leoric’s Passage.
Go through Leoric’s Passage to trigger a cutscene with the finding of Deckard Cain.
After the cutscene, quickly run to Cain’s aid against the Royal Henchmen. Kill off the first few, then take on a few more, this time lead by the Headcleaver.
Royal Henchmen move a bit faster than Risen, and attack with basic weapons.
Headcleaver is a larger version of the Royal Henchmen, with more hit points, and an added attack: its evil laugh. It stops moving and attacking when it laughs, however, making that the opportune time to attack it.
Speak with Cain, and he’ll open a secret exit.
Follow Cain through the secret exit, and then back to New Tristram as he makes use of the Cathedral waypoint.
Report to Leah at New Tristram. The Legacy of Cain quest complete!