Dark Souls

You have to defeat the Four Kings for this achievement. They are located in the New Londo Ruins and you need to meet the following requirements to challenge them:

- Defeat the Great Grey Wolf Sif
- Equip the Covenant of Artorias ring you obtained from defeating Sif
- Have the key to access the lever that drains the New Londo Ruins. There are two ways to obtain this:
1. Acquire the Lordvessel and talk to Ingward, the crimson robed cleric on top of the church-like building in the New Londo Ruins, or
2. Kill Ingward and he will drop the key. I suggest you buy everything he has before you do this. This step can be done before you acquire the Lordvessel in Anor Londo.

Once you have all these, just traverse the ruins until you find a narrow walkway leading to a fog wall. Make sure to equip the Covenant of Artorias ring before you fall down the bottomless pit to access the Abyss. Once you fall, the Four Kings will appear soon afterwards.

For an effective strategy, buy the Iron Flesh pyromancy from Laurentius (the pyromancer you saved in the depths), equip armour with high defenses (the stone armour in the Darkroot Garden is good as well as Havel's armour.) and a good elemental weapon (Lightning Spear from Sen's Fortress) or the "Combustion" and "Great Combustion" pyromancies with a reinforced Pyromancy Flame. As soon as the fight starts, run up to the first king and cast Iron Flesh immediately. Then, it's a matter of casting your pyromancies or poking the king with your spear. Iron Flesh will cut down the damage you take significantly, but remember to heal when necessary. Each king will die once you take off all of it's health, generally this is reflected as about a quarter of the big health bar. Be quick because the kings will appear slowly one by one and it is possible to be ganged up by all four of them at once. NOTE: Even if there's one king left (you've killed three of them) more will still spawn despite the name, so don't let up. Once they're down the achievement will pop.

The following video shows you how to get to the Four Kings and also how to effectively beat them whilst two handing a Lightning Spear+5. Iron Flesh is not used so it is possible without it in case you did not obtain it.

EDIT: As of patch 1.05, Iron Flesh has become much less effective, so it's up to you whether you use it or not. Find the best strategy for yourself.

In both of my fights against The Four Kings (NG and NG+) I've noticed that a shield is not even needed as it only really hinders your progress in the fight.

So what I myself did was go all out tank on them. It may not be the most elegant of strategies but it works. For NG I wore full Havel's armour and the lightning spear (+5 I think) was my weapon. Simply run at them, rolling the opposite direction to the way their sword swings and use constant 2 handed attacks on them. Keep an eye on your stamina though so you can still roll/run away from the AOE.

I noticed that whenever I got hit from their attacks it didn't take a ton of health off so pop a flask and you should be ok. On NG+ the fight was a lot harder and took me many tries (unlike my TWO tries on NG!). I used the shield that regenerates stamina faster (grass crest shield I think) and to keep my rolling fast enough I only had on half of Havel's armour, which was still good enough defence. And I wielded a 2 handed gravelord sword +5.

In a nutshell, if you want to do this kind of method:
-Don't bother with your shield. Use the grass crest shield if you want fast stamina regeneration which helps A LOT
-Have high vitality and endurance as you can do more attacks and also take more hits without worrying too much
-Have a good armour set. Havel is what I used but Smough/Stone armour should suffice
-Know how to roll! It's quite easy to dodge their sword attacks if you time it right so keep at it
-Have a high damage weapon, and a fast weapon is recommended like the lightning spear. This boss has a ton of HP so you'll need the best weapon you can find
-Finally, have a decent amount of estus flasks (upgraded ones at that). This tanking method can cause a lot of flasks to be used so be prepared!

Hope this helps a few people who fancy tanking The Four Kings!

Pyroskank's solution gives a good outline of how to reach the battle, but in the interest of keeping things together, i'll outline it again:

You must reach the end of New Londo Ruins after completing the following steps:

1. Defeat Sif and obtain the Covenant of Artorias
2. Acquire the key to Lower New Londo from Ingward.
3. Make your way throughthe final fog door, equip the ring and jump into the abyss.

The Four Kings battle consists of a series of 4 individual enemies that share the one boss health bar. You will start by facing only one and the rest will appear after set intervals. The Kings have 3 main attacks: A Sword Attack, a Homing Magic Attack and a AoE Magic Attack.

The most important piece of the strategy for this fight is this: Stay as close to the king you are fighting as possible! If you stand right next to the king, the sword attacks will do next to no damage and he will never use the homing attack, so you only have to worry about the AoE (For my build, this attack took about 1/2 of my Max HP.) Best of all, I found that if the next king appears before you have defeated the previous one, it will not engage you as long as you remain up close to the first. (This may not last forever, but I spent too much time trying to dodge one of the homing magics and hadn't even hurt the first king when the 2nd appeared and he didn't try to attack me.)

So the fight goes about the same as Pyroskank says (I also used the +5 lightning spear (~250/hit), two handed with the grass crest shield) but you don't need Iron Flesh or Heavy Armor. As long as you are close enough, it doesn't matter. (At least, it didn't for me!) Just make sure you heal whenever you get close to 1/2 HP and right after he does the AoE attack.