In daylight, that same spot looks like this:

Immediately in front of The Poorman is a stone on the ground. That stone is the secret marker for spawning Mephisto. The Poorman walks up nearly to the point of touching it:

The first of Mephisto’s minions immediately surge up out of the ground. A second later Mephisto appears between the buildings just North of the stone. The Poorman has only an instant to initiate a flurry of Smites before Mephisto will cast his devastating lightning attack. But The Poorman has been hunting monsters for long years in the wild, and he knows that if he engages Mephisto the fight is over and The Poorman is dead. For to close with Mephisto he must close the gap between them, and the instant he steps beyond the stone he spawns Diablo and probably Baal as well. Against Mephisto alone he has a chance; against all of the Three together he is badly overmatched.
So he does the opposite of what Mephisto expects: He runs away, toward the bottom of the screen. Sensing an easy kill Mephisto leaps forward himself, momentarily outracing his own minions. The Poorman readies himself for that surge. Quick as a thunder crack he must whirl to face Mephisto, toggle to the hotkey for his bone wand’s Life Tap charges, right-click a Tap charge on Mephisto’s head, hotkey back to Salvation and hold down on left-click targeting of Meph to initiate a sustained Smite attack.
He either does that correctly or he dies. To get a Life Tap cast he must get the skill on his right button, and for as long as it’s there his Salvation is off. While it is down he stands exposed to Meph’s Conviction. The excess LR he wears (Orts in helm and armor and 29% in a grand charm) sustains his defense against lightning, but his cold and fire resists drop well below max and he takes damage much faster until Salvation goes back up. If he rushes and gets Salvation up before a successful Tap sticks to Meph then his resists are fine but he has zero leach. He can gulp pots in a desperate effort to keep up with the onslaught raining down on him, but 12 pots don’t last long in that extremity and when the last one is gone he is done for.
The Poorman knew this moment would come. He trained for it in Durance against Mephisto’s Act 3 cousin. His moment is now at hand, and as Uber Meph races toward him The Poorman casts Tap, brings Salvation back up and locks Meph in a Smite attack. He now has 28 seconds of Life Tap with uninterruptible 7-frame Smite attacks, connecting 3.5 times per second, leaching an average of 518 life points per second. Even that much leach cannot keep him alive, but it dramatically extends the length between fat purple quaffs.
The Poorman knows that with his lowly crown shield his Smite attack (about 370 hp per attack) barely tickles Meph’s 650,000 hp life bar. But Meph is maniacally determined to kill the warrior he towers over and won’t disengage even to save himself, while The Poorman has the inexorable force of mathematics in his arsenal. Unfortunately for The Poorman, the laws of mathematics dictate that he cannot kill Meph within the 28-second window that is now available. So The Poorman counts down the seconds aloud while the battle rages all around him, and whenever his life ball takes a precipitous hit he spends a precious purple. “ . . . 21, 20, 19,” “. . . 12, 11, 10,” “. . . 7, 6, 5 . . .”
At the count of ‘3’ The Poorman executes his life-or-death sequence again: Tap charges up/cast Tap/Salvation back up/lock Smite attack on Meph. It costs him nearly a full second and another fat purple. But The Poorman has Meph back in the unforgiving embrace of mathematics, and this time it is Meph who cannot outlast the clock.
Somewhere in the recesses of his vile mind Meph must sense that something is wrong. His life bar is down to a sliver, less than a tenth of where it began. For while he has been raging against the small paladin in front of him, barely noticing the puny physical damage from his shield, Meph has overlooked The Poorman’s lowly boots. Goblin Toes have but one useful attribute: 25% crushing blow. With another 8% cb on his crafted gloves The Poorman is landing just over one crushing blow per second. Meph’s weakness is physical resists (he has only 20%), so each crushing blow removes one twentieth of his remaining life.
Meph has never worried much about his physical resists because he starts with an enormous life pool and regenerates lost life many times faster than his enemies can remove it. But once again Meph has overlooked a humble part of The Poorman’s garb: His belt, with its 10% chance to cast Open Wounds. Meph is vulnerable to OW, and OW works with Smite. Once triggered it lasts for 8 seconds, and at a rate of 3.5 attacks per second it is all but impossible for Meph to get out from under its grasp. So for every second of the fight Meph has lost a twentieth of his remaining life, and at the half-minute mark it is nearly gone.
Now it is too late for him to worry about crushing blows, and their effect no longer matters. Of the few thousands of hit points left to him the loss of a twentieth hardly registers. But the puny direct physical damage of the shield’s Smite attacks now comes to the fore. A 370-hp attack was laughable against a 650,000 hp life bar. But with just a few thousand life points left and 3.5 of those attacks per second, Meph is not laughing. His only hope is to kill The Poorman before his dwindling life source expires.
But The Poorman’s 12 purple potions last long enough and his resist maximums are high enough – barely – to bring Meph down. The demon crashes to the earth in ruin. His minions continue attacking half-heartedly but are in disarray. The Poorman takes his time and dispatches them one by one, making certain to draw each one down to the Southwest corner of Tristram first so as not to accidentally spawn Diablo or Baal. The Poorman retraces his steps back around the perimeter, taking the red portal up to Harrogath.
He repairs his gear, refills his belt and replaces Iratha’s Crown with his 3 P-ruby crown, gaining 114 life in exchange for lightning and fire resists that he no longer needs. He replaces the LR and FR charms in his Inventory with the life charms stored in his Stash to gain 46 more life. He leaves one inventory slot open.

He gulps more antidote and thaw potions, dons Treachery again and triggers Fade. He puts Darkglow back on and recasts Holy Shield. Now he sets his aura to Fanaticism. Salvation has served its purpose and he will not use it again.
With level 21 Fanaticism he easily has a 6-frame Smite attack, cranking 4.1 attacks per second. Fana adds 390% ED as well. But the net physical damage to Baal and Diablo will total only a little more than the slower and weaker Smites against Meph because both Baal and Diablo have 50% physical resistance compared to Meph’s 20%. Their extra physical resistance will affect crushing blow as well, so despite the greater speed and power of attacks, the damage rate against Baal and Diablo is actually a trifle below the damage rate inflicted on Mephisto.
The Poorman is ready for the second stage of the battle. He fills his lungs with cold mountain air and heads back down.
Now is the time to fight Diablo because even alone Baal will be the hardest of the Three, and for that encounter The Poorman wants all of Tristram to maneuver in. Drawing out just Diablo is trickier than with Meph, but once again The Poorman’s canny wile serves him well.
He circles the Tristram perimeter just as for Meph, and approaches the same stone on the South side. But this time he goes a full step beyond it. He inches forward just until Diablo’s minions begin to spawn. Even then, when he can see the light emanating from Uber Diablo at the top edge of the screen, The Poorman goes no closer. Diablo must be coaxed out beyond the buildings. The Poorman now must run back and forth until Diablo’s fickle AI drives him out to fight. If The Poorman stops running while trying to lure out his foe, Diablo’s bone prison can trap him like a juicy morsel in a cage. Yet if The Poorman encroaches closer to Tristram’s buildings he may spawn Baal as well.
After 10 or 15 tense seconds jogging back and forth (and dodging Diablo’s Pit Lord minions), Diablo charges out to fight. It is the last mistake he will make. Alongside either of his brothers the attacks of Uber Diablo are ferocious. But when The Poorman can close on him separately Diablo is vulnerable. The Poorman casts Life Tap on him and commences to Smite. The Pit Lords, with their unbreakable immunities to all 5 forms of magic damage, are so big that only a few can crowd around close enough to attack, and they cannot distract The Poorman while Life Tap is up. After 24 seconds The Poorman recasts Life Tap, restores Fanaticism, and pounds on Diablo until he collapses. The Poorman disengages from his minions and again, one by one, Smites them to death in the Southwest corner of Tristram (the sole vulnerability of the Pit Lords is that they have just 50% physical resists). The whole encounter with Diablo has cost just a single fat purple potion.
The Poorman returns to Harrogath and rests briefly. He goes through his pre-fight routine: Repair gear, gulp more antidote and thaw potions, trigger Treachery and put Darkglow back on, cast Holy Shield and set his hotkeys to Smite/Fana. Then he makes a crucial adjustment, replacing the leftmost belt stack of fat purples with blue mana pots.
The fight against Baal will be by far the hardest to survive. The Poorman pauses to think how to make best use of the terrain. He decides to challenge Baal on the East side of Tristram, a short space South of the red portal.
To spawn Baal he has a choice. He can circle counterclockwise all the way around the perimeter to the Southeast corner and approach the gap between the buildings there, or he can head due South from the portal and spawn Baal as he runs Southward. The second option is quicker and The Poorman takes it. After just a few paces Baal and a host of his minions spawn and charge after him.
The Poorman executes the retreat/Tap/Fana/Smite sequence and locks up with Baal. He then makes two unpleasant discoveries. First, his mana ball goes empty almost at once; Uber Baal drains mana as often and easily as his Worldstone cousin, so The Poorman guzzles a blue pot. Second, the Specter minions are more dangerous to him than anything in the supporting cast of Diablo or Meph. Though they hovered on the periphery at first, once The Poorman closes with Baal the Specters circle in and attack. Baal has summoned six of them (or so it seems to The Poorman as he counts them out of the corner of his eye), and they stack on one another so all of them can combine into what is effectively a single massive attack. That by itself is bad, but even worse is that they also suck The Poorman’s mana ball bone dry. He now has Baal in his face and six Specters on his back, and the whiffing sound of his swinging shield fills the air because he has no mana to connect with Smite. His red ball takes a huge hit. He pops a purple and gets a few good digs in on Baal. Then his blue ball goes instantly empty. He pops his second blue pot and continues.
Just seconds later it happens again. He uses his last blue pot and has a few productive seconds to whittle Baal’s life bar down. But as soon as the blue pot’s regeneration is done his mana ball is sucked dry, and now he must drink purple pots to refill it. Baal and his Specters empty it mere instants after it refills. With Baal’s life bar only about half gone The Poorman knows he cannot win. Whenever his mana ball goes empty he cannot leach and is vulnerable to everything Baal and his crew are throwing at him.
The Poorman breaks off the fight and takes the portal to Harrogath. He goes through the same pre-fight steps and returns to battle. Baal’s life has regenerated to full. The Poorman casts Tap and closes. After 30 seconds the results are the same: He is nearly out of potions, he has twice come within a sliver of dying, and Baal still has a sizable chunk of his life bar intact. For the second time The Poorman breaks off and retreats to town.
He is exhausted and he is frustrated. But he is not yet beaten.
He will face Baal one last time, and will return either victorious or not at all. He goes through his pre-fight steps, checks his gear, and drops down the red portal.
The flock of Specters foiled his initial strategy, so he takes them on first. They are physically immune and he has no magic or elemental damage to wield against them. But he has a keen mind, whereas the Specters are rather dim.
He edges far enough from the portal for the Specters to see him, then turns and runs into the center of Tristram. The Specters follow like pets on a leash. The Poorman runs West across the square and between the buildings on the West side. The Specters trail behind him.
As soon as he clears the last building The Poorman cuts North, with his right shoulder along the West wall of the Northwest building. The Specters float out from behind him, but take a second to spot him again and turn North in chase. By then he has reached the Northwest corner of the same building, and cuts sharply to the right so as to duck out of the Specters’ line of sight.
Now they are confused. They drift listlessly Northward, but have lost his scent. They hover on the West side of Tristram, unable to spot where The Poorman has gone.
The Poorman knows where he is going: Straight back to Baal, who remains on the Southeast side of Tristram. The Poorman immediately re-engages him there. Baal summons fresh Specters, but only a few of them. Now the opponents are evenly matched.
As never before, The Poorman’s movements must be flawless and he must make the most of each potion in his belt. He locks up with Baal and begins the grisly work of a professional warrior. He ignores the searing pain of Baal’s attacks. The Poorman no longer sees Baal, no longer hears the sounds of combat. His stares only at his own life and mana orbs. He hears only his own voice as he counts out Life Tap’s duration. When his red ball crashes below a third he pops a purple. Five of them are already gone. As the first Tap charge is about to expire he renews it and begins the count again: “28, 27, 26 . . .” Twice his mana ball goes dry and twice he spends a blue pot. “16, 15, 14 . . .” Flurries nearly overwhelm him three times more, and he staves each one off with a fat purple.