Mephisto’s Abilities and the best strategy to beat Him at the end of Act 3
Dul’Mephistos or the Lord of Hatred is one of the three Prime Evils. He rules over the Realm of Hatred in the Burning Hells. You can find Mephisto at Durance of Hate’s 3rd level. Before you can encounter him, you have to battle a group of Bloodlords and some Council Member Bosses. Then, you can reach the Boss either by following the right or the left path around the pool of blood. There is a Unique Council Member Boss in both rooms.
After the events of the Sin War, the Lesser Evils were disappointed, believing that the three Prime Evils had forsaken the Eternal Conflict in order to focus on humanity. Later, the Lesser Evils opposed to the three Prime Evils. Despite Mephisto’s and his brothers’ efforts, they were sent out of Hell, into the mortal realm (known as Dark Exile). In response to these evil beings, the Archangel Tyrael gathered some disparate Mage Clans into an alliance named Horadrim. Then, he gave them the soulstones to bind the three Prime Evils forever. However, this series of events had been plotted by the Three. They knew that the soulstones would corrupt, and as a result, the Worldstone would corrupt as well, along with all the humanity. It could be a new army to be used against Heaven’s forces.
After an exhausting battle, the Horadrim succeeded in slaying Mephisto and imprisoned his essence inside the soulstone. The Horadrim entrusted the stone to the Zakarum priests and it kept sealed in the Temple of Light in Travincal. Diablo and Baal arrived at the innermost chamber of the temple, where they found the soulstone and released their brother. After three centuries, the Prime Evils united again. Inside the chamber, the Prime Evils decided to reclaim the Burning Hells and enslave humanity according to their will. However, soon a team of mortal heroes found Mephisto in order to stop him and his brothers. After many hours of battle, the heroes managed to defeat Mephisto and imprisoned his spirit into his soulstone. Later, the artifact was destroyed at the Hellforge.
In addition, it’s a good plan to battle Mephisto in one of the rooms on the right or left in order to avoid the restless spirits. They sometimes rise up and attack characters that are in range. You can kill these spirits, but it’s difficult to hit them. Also, experience reward is low and they don’t drop any loot. Further, you should have enough cold resistance and lightning resistance for reducing Mephisto’s damage, especially if you are a melee class.
Note that in Nightmare and Hell difficulties, he’s immune to mana and life leech (unless you cast Life Tap). Therefore, you should keep some mana, health and rejuvenation potions before the battle starts. For ranged classes, the easiest way to slay Mephisto is to draw his attention by approaching him slowly and then retreat to the central room with the pool of blood. Mephisto’s AI doesn’t allow him to cross the pool and reach you because he can only move in the specific direction of the player’s position.
Eventually, you can kill Mephisto from a safe distance using Area of effects spells (like Blizzard), ranged weapons and missiles. Your hireling and your minions would probably die as they will go close to the Boss, but you will be safe as long as you don’t approach him. After you defeat Mephisto, you can search the room for stashes of gold. He will also drop his soulstone, an item that you need for a quest in the 4th Act. If you don’t retrieve it, Deckard Cain will offer it to you later.
Then, a portal will open and a bridge made of skulls and bones will rise from the pool of blood. You can cross the small bridge and pass through the Infernal Gate to complete the Act 3.