Act I Minions:
Colenzo the Annihilator will be leading the Act I Monsters, a bunch of warped Shamans. He's fire enchanted and immune to fire, but otherwise very weak. As long as you don't' expect your firewall to do the job single handedly, Colenzo is no threat.

Act II Minions:
Achmel and his army of Unravellers represent the sect from Act II. These guys can deal a Poisonous attack and are immune to Poison themselves. As long as you don't rely just on a Poison attack, they are fairly harmless.

Act III Minions:
The squad from act three gets a little more dangerous, featuring half a dozen Council Members led by Bartuc the Bloody. Bartuc is not only highly lightning resistant, but also Lightning Enchanted. Whatever you do, don't charge straight into the fray and start hacking at Bartuc, the charged bolts will probably kill you. Instead, calmly proceed to eliminate his minions first, then attack Bartuc from an angle where the charged bolts won't strike you. Remember, the only threat here is the charged bolts, the Council Members themselves are of too low a level to be able to hit you.

Act IV Minions:
The Act IV Minions are actually easier than those of Act III, provided you take care not to get yourself surrounded. Ventar the unholy is featured here, leading a squad of Venom Lords. As their name would suggest, these guys are completely immune to Poison. In addition, you'll find them to be highly fire resistant. Other than that though, they ain't much to worry about.

The Minions of Destruction are the toughest monsters you'll face in Diablo II. To make matters worse, they'll be able to get a dozen free hits on your while your computer loads their hefty graphics.

Minions of Destruction:
The fifth and final squad of Baal's personal guard are the Minions of Destruction. These monsters are unique to this mission and extremely powerful. Each single minion as strong as an unique monster, and their leader, Lester the Tormenter, is more deadly still. If you have a melee Mercenary, expect him to die here. The Minions of Destruction feature a stunning attack that render you mercenary pretty useless.

One major difficulty you'll face in this level is the computer lag. Since each of the monsters that Baal summons were previously unseen in Act V, your computer will be forced to load their graphics on the spot. Consequently, those on slower systems can expect their computer to freeze for nearly 10 seconds while Baal summons the next group of defenders.

While this may not be a problem in single player, it does mean that your character could be dead before you regain control of your character. This is especially the case when Baal Summons his minions of Destruction. Therefore it is highly recommended that you retreat all the way out of the Throne room while fighting the Venom Lords, as to avoid being killed before you can land a blow.

Necromancer Tip:
The Minions of Destruction, despite being powerful, are only melee attackers. A Blood Golem with the aid of Iron Maiden should be able to kill them eventually.

Sorceress Tip:
Set the throne room burning, so that any minions that Baal summons are set ablaze, even when your computer is still frozen.

Once all his minions are defeated, Baal will activate the portal to the World Stone Chamber. Once you're restocked and ready, follow him for the final battle.

Destruction's End:
Baal is surprisingly easy for the very last boss, certainly easier than Diablo, and I would venture to say easier than his minions as well. Don't get too relaxed though, this doesn't mean his a complete push over.

Baal doesn't attack very quickly, nor does his have a lot of hit points. The key to killing the Lord of Destruction is to attack him hard and furiously till his dead. Concentrate on dealing the damage with one hand, and drinking potions with the other. Ignore the surrounding tentacles and keep hacking or shooting at the boss. You want to destroy him before he succeeds in creating duplicate of himself. Once there are two Baal's on the loose, things become a lot trickier.

Baal can hurl a number of different elemental attacks, including a wave of cold that'll knock you backwards, a fire nova reminiscent of Diablo's own and a concentrated beam of intense energy. As long as you have your Ancient's Pledge Shield ready from Quest 2, you shouldn't find too much of a problem resisting these attacks… Provided there's just one Baal that's firing them.

The trick to killing Baal is to make sure he doesn't have a chance to create a clone of himself. Here, a necromancer uses a combination of high level Lower Resist and Bone Spear to deal the damage as fast as possible.

Sorceress Tip:
Static Field all the way! Teleport up to the Lord of Destruction and cast it like no tomorrow, his life will go down extremely fast. Once he's almost dead, summon a few Hydras and teleport away. This way, you're almost guaranteed to kill Baal before he makes a duplicate.

Necromancer Tip:
When you see Baal, summon a Fire Golem right next to him. Within over a thousand hit points, your golem should be able to buy most of the time you need. Curse Baal with Lower Resist and send in barrages of either Bone Spear or Bone Spirit till his dead (Bone Spirit is more preferable).

Barbarian Tip:
Use Leap Attack to get near Baal, then just use whirlwind. In 800x600 res, you'll be able to leap from the central pedestal to either side to retreat if necessary.

Assassin Tip:
Charge up your attacks by bashing on the tentacles, and then assault Baal directly with Dragon Flight. Follow up with Phoenix Strike and Dragon Claw.

Paladin Tip:
Vengeance and Fanaticism will do the job here, just keep hacking and drinking potions.

Druid Tip:
Your minions will make good canon fodder. While Baal is occupied, rip him apart in werewolf form with Fury.