Blaue Kathedrale

Your first step into the Cathedral of Blue begins with a boss fight. Right before the mist is a corpse with an Old Radiant Lifegem x1 and an iron chest with a Ring of Binding and x5 Human Effigies. Step through the mist to take on a familiar foe, the Old Dragonslayer.

Boss: Old Dragonslayer

Welcome back! Wielding armor and a spear very similar to Ornstein's Dragonslayer Spear from the original Dark Souls, the Old Dragonslayer has some new additions to his moves, including dark damage replacing his old lightning fans are used to. He leads with his spear and has a variety of moves. He is very aggressive and requires vigilant dodging from the player.

Strategy

As with the Dragonrider the key to this boss fight, for melee builds, is staying behind your enemies back. Similar to the second phase of his Dark Souls fight he will use an attack called Dark Crash Crash very similar to his Old Lightning Slam the Old Dragonslayer will begin gathering dark energy around himself this is the signal to run or roll away as fast as possible if you feel you are not far enough away back up some more, it is always better to be safe than sorry. If you fail to dodge, this attack is likely a guaranteed death.
As a ranged build your goal is to continually strafe your enemy and quickly roll to dodge when he is attacking. Against a ranged enemy the Old Dragon Slayer will us his Leaping Stab and Smash far more often, both can be dodge by rushing forward and rolling straight under his attack. At Ranged the Old Dragonslayer will also begin to use two new attacks his Dark Shot and Dark Triple Shot which are both variations of the same technique. For the Dark Shot the Old Dragon Slayer will hold his spear above his head and begin charging energy this attack actually has a bit of an arc, so like his Leaping Stab and Smash, be dodged by rushing forward and rolling underneath the Dark Orb, be warned though if this technique is used be prepared to quickly dodge any following attacks, the Dark Orb can also be dodged by carefully rolling to either side or completely blocked by one of the many pillars in the room. Dark Triple shot is similar but with few options for avoidance the Old Dragon Slayer will once again begin charging his spear however this time he will point his spear in front of himself and then he will fire three identical orbs is a fanned spread, your only options for dodging this attack are once again to rush forward and roll under the orbs or quickly run behind a pillar and use it to absorb the impact, if you manage to be hit by all three orbs death will most likely soon follow.

Drops:

Attacks/Moves

Spear Swings: the Old Dragonslayer's most common and weakest attack can be both blocked or dodge by moving behind his back. If you are feeling flashy the attack can also be parried fairly easily by blocking the first swipe and then parrying on the second.

Quick Swipe: Takes a single swipe and then leaps backwards.
Leaping Stab: a quick and powerful leaping stab easily dodged by rolling forward, can also be blocked with enough stamina.

Leaping Smash: a powerful leaping smash similar to the leaping stab but slower. Suggested to roll forward do no try to block.
Impale: a very powerful charge, when he is low on health the Old Dragonslayer will begin using this unblockable technique. Signaled by his spear being raised into the air then quickly lowered.
Charge: will touch the ground with one hand and draw the other behind himself before rushing forward, attack can be blocked with enough stamina or parried with correct timing.
Two-Handed Spear Thrusts: a very dangerous technique which will quickly drain all stamina if blocked fully. The Old Dragonslayer will hold his spear and two hands and perform a quick forward thrust followed by a slower and more powerful second thrust. The best way to handle this technique is to block the first hit and roll forward on the second you will roll underneath the second lunge giving you a perfect opening to deal some damage as the Old Dragonslayer recovers his poise.

Dark Shot: a powerful ranged energy attack, signaled by the spear being raised above his head and then being charged with dark energy.
Dark Triple Shot: a triple shot version of Dark Shot in a fanned spread pattern, signaled by the spear being pointed forward and then being charged with dark energy.
Dark Crash: a very powerful AOE signaled by the Old Dragonslayer gathering a large cloud of dark energy around himself.

Backstep: Quickly leaps backwards.

Killing him allows you to go to the balcony ahead. A wooden chest to the left holds Cracked Blue Eye Orb x3 and an iron chest to the right contains a Heide Knight Iron Mask and a Tower Shield. Blue Sentinel Targray looks over the balcony. If you have successfully been summoned to another player's world and defeated the boss(as a phantom only, does not count as a shade), the NPC will offer you a covenant with the Sentinels of Blue. You can also elect to kill the Knight of Blue, which results in him dropping the Blue Knight's Halberd. On the right before the balcony is a staircase down which leads to a bonfire.