Siegward of Catarina is an NPC in Dark Souls 3 who can be found at Undead Settlement where you passed Eygon of Carim, and he will be coming up the lift. Exhaust all the dialogues after meeting him and he will move to a ledge nearly at the top of the lift, but you need to roll off if timed right and speak with him again. To Trigger his side quest, you must first assist him to fight the Fire Demon here to get some gestures and a Siegbrau.
Siegward of Catarina NPC Quest
Just make sure you talk to him when you first saw him on the elevator or else the game will despawn him and when you go to the Fire Demon, his dialog will appear, and he will join you to fight the demon. Once you reach the Cleansing Chapel bonfire in Cathedral of the Deep you will find him again trapped in a well and you must get his armor to receive the Rejoice gesture.
The Second Quest
After saving him from the Well you again encounter him at Irithyll of the Boreal Valley, through a small sewer connected to the lake near the Distant Manor bonfire, resting by a fireplace. You can share some Estus soup and toasts and get gestures here if you missed them in the first encounter (Toast and Sleep). Reach the Profaned Capital and continue until you climb the structure here and grab the keys at the end of the path.
Using the Old Cell Key frees him and nets you a Titanite Slab and also find Covetous Gold Serpent Ring in his cell. Continue with you exploration trigger the Boss fight with Yhorm the Giant where Siegward will assist you. After the fight, you will receive the final Siegbrau then Escape the area. To Find Catarina Set and Stormruler Sword head to the area where Siegward was sitting.
This was all about Siegward of Catarina NPC Quest if you want to know more other NPC quest, walkthrough, and collectibles location then make sure you visit our Dark Souls 3 Wiki Guide.