This is definitely one of the more challenging battles in the game, since it's 2-on-1 unless you summon Solaire to help or other players. Both the bosses are aggressive and upon killing one, the other one gets a power-up from the other boss; if you kill Smough first, then Ornstein will become very large and if you kill Ornstein first, then Smough gains electricity for his attacks. It is highly recommended to have both good physical resistance and electrical resistance for this fight, just in case. Smough only has four attacks, two of which can be easily avoided by sticking right up against him; the first is a left to right hammer swing and the second is a vertical smash with his hammer. A third attack is him charging you and then swinging his hammer upwards, knocking you in the air; sometimes, he might chase you farther than normal, but as long as you roll backwards just as he begins swinging, you should dodge this. The final attack of his should be familiar if you remember the Asylum Demon, as he butt slams the ground; the damage is pretty big for this attack and the range is bigger than Asylum Demon's attack, but it's not hard to avoid as long as you step/roll backwards. Ornstein has a variety of attacks, and he has a few that can be very quick. He has two attacks where he throws a lightning bolt at you, one that is a little slower and homes in on you (he charges it above his head) and the other is quick and straight (he charges this one at his waist). He also has another attack that looks similar to his quick lightning bolt, but he lunges at you instead. He has another move where he kneels down, then quickly charges at you; block this with your shield. He also has a variety of melee attacks with his spear, like a sweeping attack that he can do again in a combo of three attacks (sweep, sweep from other side, then a vertical hit). Note that there are three pillars on each side of the room, which you should use to judge your position at any time, so you don't get yourself in a corner. You should try to stay locked on to one of the two at all times, and keep an eye on the other one at the same time. You can use the pillars to your advantage, too, as you can block one of the enemies' attacks with it while you concentrate on the other. If you fight Smough second, there's a big chance to hit him after he does his vertical hammer smash. If you fight Ornstein second, you should stick to staying underneath him unless he jumps up and does the butt slam, which sends out a little electric shockwave.