Black Iron Tarkus
In the room across the bridge to the right of the boss' fog gate.
- It is possible to be picked up and thrown off the arena and surviving, resulting in the player being stuck down off the main area.
- Physical attack
- Horizontal slash that shoots out a blast of energy, knocking the player back. Seem to only happen if the player is very far away from him.
- Horizontal slash. This is sometimes followed up with a backward slash, in case the player moves behind the golem.
- Vertical slash in front of him.
- Stretches his arm out, and then grabs in between his legs. If the player is caught, he will be picked up and thrown to the ground. This deals damage both when caught and when hitting the ground.
- Stomps one of his feet 2-3 times in a row.
- Punches the ground in front of him.
- If the player is too close, the Golem will jump away from the player.
- Kill the firebomb-throwing Giant before the fight, else he'll throw firebombs at you, making the fight harder.
- Try and stay close to the Golem and hit him from behind while he's recovering from his attacks. Be careful as he may grab you if you stay underneath him for too long. You should be hitting him once or twice and then moving away. The biggest opening for attack is when he's stomping his feet, just hit the other foot. But you can basically get hits in after every attack.
- Always try to keep him in the middle of the platform, and move away from him if he gets too close to one of the edges of the platform that you're fighting him on. There is a serious risk of being thrown off the platform since all of his attack push you back even while blocking. Most likely, this will be your main cause of death.
- If you run to his unarmed side, he'll try to grab you. This is the most likely lethal of his attacks since it can be tough to dodge and does very high damage. Staying on his axe side will cause him to use a frontal axe attack instead. This move can be dodged easily, but it will most likely completely miss if you continue to circle his axe side. As above, blocking is very risky.
- Almost all of his attacks can be dodged by running between his legs. For one of his attacks he will wind up and swing his axe like a golf swing, keeping his legs together. If he does this, get close and circle him in the direction he's winding up, and he will easily miss you. If you run through his legs make sure you are positioned so that your attacks will hit his legs. Since the lockon targets his chest which is high off the ground, you might find yourself hitting air if you don't position yourself properly.
- Attacks are very slowly and moves are telegraphed clearly. Therefore, a no (or low) armor, no shield, "hit and run" strategy is viable. Adjust your equipment burden so that you move as fast as you do when naked and two-hand your weapon. Attack the feet once or twice between each Golem attack. When he leans on his hand, attack as many times as you can.
- In the first playthrough, Black Iron Tarkus is strong enough to kill the Golem himself. Summon him if you want to speed up the boss fight or you just having a hard time fighting the Iron Golem.
It is possible to make the Golem fall right off the tower, resulting in an instant victory. Attacking the legs enough times in a row will cause the Golem to stagger, and attacking him when he's staggered will make him fall backwards. If you do it near a ledge, he might fall off the edge, instantly killing him. Use high damage weapons (like ultra greatswords) or Power Within to quickly stagger him. If you're really lucky, Tarkus (and the Golem's A.I.) may do this for you (video).
No spells or firebombs needed. Recommend having at least 10 Estus Flasks and the highest damage weapon you can use and still have a fairly quick recovery time.
This fight is Dark Souls' way of teaching you two things: 1. Getting thrown off is an easy way to die, no matter what your level is. 2. Locking on isn't always the best solution. The latter is especially important here, as locking on will cause you several problems. Your camera will get wobbly and glitchy when you have to go between the Golem's legs, you will have a harder time hitting his legs, and you will be less able to know where you should be rolling to since you will always be looking at the Golem's crotch. Ditch the lock-on for this battle.
As soon as you enter the fog door, immediately start running straight towards the Iron Golem. The first thing the Iron Golem will do is his horizontal slash that sends out a blast of energy. If you were quick enough the Iron Golem's energy blast won't even come close to hitting you. It is also possible to walk just a few steps after entering and let him send his blast attack. If you're at the right distance in front of the few little steps, the trajectory of the energy blast will cause it to hit the ground and dissipate. You will then be able to just run normally to the Golem to get into fighting distance.
Once the Iron Golem is on the platform you want to stay maybe 10 feet away from him. From this distance he will almost always do a horizontal slash. This is very obvious as his stance will change and he will begin raising his left arm (the one with the big fucking axe). Once you see this immediately start running for his junk. The attack is so slow and hits so far forward that you will not have to roll to be safe. He will have a large recovery time that will allow you to get 3 or 4 (riskier) hits in to his legs. Once he begins to recover, get a little distance from him as he will usually hop backwards, do a foot stomp, or a grab move. A quick dodge roll to the left or right should be more than enough to avoid all of these. Make sure you're rolling away from the Golem, since his grabs will get you during your roll if you're between his legs. Move back to his front, maintaining the same distance as before, and repeat.
Although it might be tempting to use the shiny Lightning Spear you just got for this boss since it does 54 damage per hit on the Golem and has served you so well this dungeon, resist the temptation. Because you're hitting the Golem's legs, using a spear will be fiddly and more likely to miss, and thus more likely to lure you into going for more attacks than you need to, and thus more likely to get you grabbed or thrown off the tower. Go for a wide arc slashing weapon instead.
After slashing at his legs for a bit of time he will be stunned (he'll look like he's wobbling left to right) and this is your cue to go two-handed and go to town on his legs. If you do enough damage he will actually fall over for a while, and this is when you can really wail on him. Feel free to equip your Lightning Spear or other massive weapon and attack him for all it's worth. If you're good at targeting the Golem's legs, you can get this to happen twice during this fight.
Alternate Melee Strategy
It is also possible to get behind him, and simply walk along with him when he tries to turn around to hit you.
This way you never have to worry about blocking or rolling under his attacks for the entire fight and you can focus on the damage by holding your weapon 2-handed (Did this with the Lightning Spear after a few unsuccessful tries with the standard strategy). If he tries to get some distance by jumping back, you will only need to rush to his right side (the one holding the gigantic weapon) with a few side-steps/rolls and get behind him again. (Video).
Direct Melee Combat (light armor/moderate difficulty)
In case you have trouble with one of the prior strategies, or prefer direct combat with light gear (use Havel's Ring to use heavier armor for additional defense), equip a quick vertically slashing weapon e.g. the Iaito Sword, which can be obtained in Blighttown. The vertical slashes are important because you will want to hit the Golem properly while fighting up close and you can score hits when he tries to jump away fairly often. Contrary to being mentioned above, keep you lock on the Golem at all times. The camera stayed fairly steady in my case and helped keeping me focused on the Golem's movements.
Start the fight by waiting at the fog gate for the Golem to execute his ranged attack, then position yourself in the center of the combat area. The Golem will move towards you and never use this attack ever again because we will try to stay in his melee range where his attacks are easier to dodge and predict. Whenever the Golem tries a horizontal attack with his axe, roll in the direction of his swing. Because of the huge body and wide swinging arc, the axe can only hit you in front of him and to his right (your left). This only works to some degree with his grab and punch attacks so it is recommended to roll backwards an keep your distance. When you see him preparing his stomp attack, either move behind him or back off. Though he only stomps with his left foot, you do not want to get caught up in the attack while retaliating so it's better to play safe and keep off of his right side.
The vertical swing is probably the most dangerous attacks because of it's massive damage and long reach that might catch us off guard when backing off to drink from the Estus Flask (preferably +2 or +3. I had to use one with +1 but the Golem won't hit us that often anyways). The grab attack is easy to predict and has almost no range whatsoever so in theory it's more dangerous but during the fight it's one of the easiest to dodge and retaliate. You won't need a shield so holding your weapon with both hands helps speeding up the fight. The Grass Crest Shield will add its stamina recovery boost even when just carried on the back so I recommend it for this fight since it can easily add one additional attack to your retaliation combo by waiting a little (a bit risky depending on the previous attack of the Golem) making staggering more likely.
Note that you will be moving around a lot to avoid the attacks, so keep track of the ledge, which was the main cause of death for me because I misjudged the distance and rolled straight off the platform. When being forced into a corner hug the Golem's leg to force a short range attack that causes the Golem to turn towards your direction. Usually, this will make way to return to the center of the area by rolling past the attack. Stay off the bridges because you will be forced to try rolling between the legs of the Golem, and might cause you to fall off the edge.
Fighting the Golem in direct combat will likely cause him to stagger at the edge, because the fight forces you to move around a lot which automatically makes you dance around the edges to avoid the wide arching attacks or to retaliate after doing so. It seems the Golem will always position his back to the edge when staggering in reach (confirmation needed) so you won't need to worry about having him falling into the wrong direction.
This works for sorcery and pyromancy. Keep him in the middle of the platform, have your catalyst/flame in your main hand and a good shield with 100 physical in your off hand. Circle to the right around him and dodge to the right as he swings. After each swing you should be able to get off one or two spells. If he goes in for the grab you can still dodge to the right and avoid it.
Warriors of Sunlight will be able to use their Lightning Spear Miracles to exploit the Golem's lightning weakness
Another method of defeating him as a caster is to stay at max range while casting spells, backing up as necessary. Once your back is against the wall on the long platform and the Iron Golem is getting close, run through his legs to the other side and repeat in the other direction. It's very easy to never get hit by doing this.
If you have power within and great combustion you can very easily kill the golem. First turn on power within then sprint directly up to it before it leaves the walkway it starts on and use great combustion on its leg until it falls off the side. This method is risky to perform but will result in an easy win if done correctly.
With a good enough bow and light equipment you can kill the golem pretty easily. You can lock on to it roll back and forth on the bridge between its legs. Taking a few rolls backward gives you time for 2-3 arrows. Just be careful not to fall off.