The Skeleton King
The Mad King of Tristram is back to wreak havoc on the world. He is the first major boss of the game, and as such, is the easiest to defeat. The King is a powerful melee brawler that also has a few mage-like tendencies.
With this in mind you’ll want to approach him with caution. Characters like the Monk and Barbarian should be hesitant to get too close to him. They should be ready to disengage quickly when he starts swinging his mace around. You’ll know when to run when you see the blue spirits swirling around him.
His attacks are slow but powerful and without proper backup he will take you out of the fight quickly. Long-range characters will have an easier time in this fight. They should stay at a distance and pelt him with magic or arrows. Since he is slow, you should have no problem evading most of his attacks. Watch out for his teleport though, there will be no real cue for it until he is beside you swinging around his mace.
If you’re soloing him it will pay off having a spell that can get you out of trouble quickly like Leap or Breath of Heaven. Occasionally he will summon groups of skeletal minions, but you will not have an issue with them. They are weak and are only there to distract you. Keep at a distance and constantly spray the King with damage to bring this skeleton ruler down.
The Flesh Carver welcomes you into his home and has a nice toasty barbeque planned for you this evening. One of the biggest issues during this fight is the fiery floor. Sections of the ground will periodically light on fire for short durations of time. Standing in the fire is very hazardous, and will drop your health quickly. Keep a watchful eye for the glow indicating things are about to heat up, and do your best to get to a safe section.
The boss himself is very similar to the Skeleton King. He is typically slow and hits very hard so ranged characters, again, will fare better during this fight. He comes equipped with moves that will help him get closer to you, such as his charge. He also throws red chains that will cover a cone-like area and tosses out his blue hook to pull you in.
The charge isn't bad, and can be easily side stepped, so don't worry too much about it. It’s proceeded by a red, fiery line which gives you plenty of time to get out of the way. The charge also stuns The Butcher after the attack, which gives you ample opportunity to do some damage.
The chain area of effect move will likely hit you, but it is fairly weak and even a wizard would have no problem eating the hit.
The third move is the real tricky one. He will throw his blue hook to pull you into him, followed by a powerful melee attack. There is a short animation of him pointing his meat cleaver forward before he cast out his hook. You can outrun this move but it is difficult and you will need a lot of room to do so. For a great example of this attack consult the video and make sure to pay close attention around the 55 second mark. With quick thinking you can dodge the attack but you don’t have much time.
The Butcher has a good amount of health, and it will take some time to wear him out but as long as you keep an eye on your enemy and the battlefield you shouldn't have any problems.