Aldrich is located in Anor Londo where Smough and Ornstein used to be. It is a challenging boss fight and can test the patience of new and veteran players alike. Hang in there, stick to the strategy and you’ll make it through. Upon entering the boss fog you’ll want to charge straight at the boss. He may try to cast some little purple balls that hover and then dive at you, but try not to focus on these for now and simply close the distance as fast as you can. When you get up to him, he will try to hit you with a melee attack (or two). Roll through it, get behind him and exhaust your stamina attacking his tail. He will slam his staff into the ground vanishing and causing an AoE at this point. You’ll want to make sure that AoE doesn’t hit you as it hits quite hard and you will want to make for the middle of the room.
Look around for him to appear and again charge him and repeat this process. At half health he will begin phase 2, coming out of the ground casting fire around him 180 degrees. He usually fires his arrows immediately so you will want to run away as fast as you can, as long as you can, rolling as needed until they end. He will most likely fire Crystal Soul Spears at you near the end, so be sure to keep dodging even after the arrows end until you get your bearings.
Sprint back to the boss, dodging his melee attack and hitting him once again in his tail. You will repeat this process until the boss is dead. A couple of notes about this fight: His melee attacks are erratic and hard to gauge, which is why I recommend rolling over blocking. His arrow attacks in phase 1 generally head in a straight line and are much shorter than in phase two so there is no need to run from them here.
Usually the boss will spawn in the opposite corner to the one he just vanished from, so look and head that direction first after he teleports. Occasionally you will get some bad RNG and the boss will spam Bow Attacks in phase 2 almost garaunteeing your death, try not to let that get to you. .
As found on Youtube