There are various NPCs summon signs you can locate in the Bloodborne expansion in order to summon them. The Summon Signs varies from location to location or fights to fights they can be red or sometimes blue you can have both which can help you assist in the game. This Bloodborne: The Old Hunters guide will provide you detail on How to Summon all the NPC, Location and their Requirements to summon.
Note: There are no Summoning signs in Nightmare of Mensis, the Nightmare Frontier, or in the Cainhurst Castle area.
Old Hunter Father Gascione - Summoned near the fountain near the burning effigy where the townsfolk gather around. We noticed that he can only be summoned her as they removed the shortcut door location behind the Central Yharnam lamp.
Old Hunter Alfred - Summons right before the boss battle in the courtyard. you can find his summon signs at the bottom of the stairs os the courtyard.
Old Hunter Henriette - From the Cathedral Ward lamp head upstairs and as you pass through the gate you will find Old Hunter Henriette near the ladder leading to the body with 6 numbing veils of mist. you need to fight with a bunch of enemies in this area in order to get to Vicar Amelia.
Old Hunter Henryk - At the fork in the road right before the boss battle area
Younger Madaras Twin - From the same Fork where you found Old Hunter Henryk, turn right and open the gate. The search of the Summon sign at your left. Here you will fight the snake-head enemy so better be prepared.
Damian of Mensis - Left of the fog gate before Rom.
Old Hunter Henryk - In the same area go to the top of the stairs, then turn right you will see the summon signs near the treasure chest among the couches.
Younger Madaras Twin - At the little ledge in between the two trees Right next to the Byrgenwerth lamp.
Old Hunter Defector Antal - Behind the last carriage before the fog gate, on the left.
Old Hunter Damian of Mensis - Kill the slugs first right before the fog gate and then head towards the summon sign.
Old Hunter Yamamura - Summon sign is to the right of the fog gate.
Old Hunter Valtr - Behind some crows near the locked iron gate.
Old Hunter Henriette - Left of the Nightmare Church lamp, near the stairs as if you were going to the Whirligig Saw.
Younger Mandaras Twin - Left of the blood pond with the two kin Giants the same place where you grab the Butcher armor set.
Laurence, the First Vicar: Valtr - Inside the doors of the chapel, just at the bottom of the stairs which leads up to the boss battle.
Old Hunter Prospector Olek - At Layer 3, in the circular area right before the blue/purple lantern gate.
Madman Wallar, Old Hunter Prospector Olek - At Layer 3
Prospector Olek and Madman Wallar - At Layer 3, near Starting lamp and another in the ravine next to some scorpion beasts.
Old Hunter Beastclaw Josef - At Layer 3, near the Beast Claw
Old Hunter Vitus - At Layer 3, just before the Abhorrent Beast boss door near the stairs you will find the Summon signs.
Old Hunter Prospector Olek - At Layer 2, After the first doors, to the left is the summon sign
Old Hunter Queen Killer - At Layer 2, Before the boss door.
Old Hunter Queen Killer - At Layer 3, Before boss Amygdala
Old Hunter Madman Wallar - At Layer 3, Left of the locked gate.
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