Anri is an important NPC that changes gender based on your own gender, always appearing as the opposite gender. The reason for this is that their quest line revolves around a marriage that is a crucial part in achieving the "Usurpation of Fire" Ending.
Upon reaching the Halfway Fortress bonfire in Road of Sacrifices you’ll encounter Anri and Horace the Hushed. Speak with them both to exhaust their dialogue and obtain the Blue Sentinels covenant.
After defeating the Deacons of the Deep:
Speak with Anri and Horace in Firelink Shrine to exhaust their dialogue.
WARNING: You must obtain 5 Dark Sigils from Yoel of Londor before defeating the Abyss Watchers to spawn Yuria of Londor in Firelink Shrine.
After reaching Catacombs of Carthus:
Speak with in the tunnel before the skeleton ball trap.
After reaching Smouldering Lake:
Find Horace the Hushed in a side tunnel near the lake entrance and defeat him for the Llewellyn Shield . Anri is now located in a path through the stalagmites outside High Lord Wolnir’s boss arena, but you should NOT tell him what happened to Horace.
After reaching Irithyll of the Boreal Valley:
Speak with at the Church of Yorshka bonfire and exhaust his dialogue to obtain the Ring of the Evil Eye .
After reaching Anor Londo:
Speak with Yuria of Londor in Firelink Shrine to exhaust her dialogue. She’ll inform you that Anri awaits in the Temple of the Darkmoon, located behind the illusionary wall in the room at the base of the rotating tower that leads to Anor Londo.
Speak with the Pilgrim to gain the Sword of Avowal and then enter the chamber and perform the ritual to obtain the final 3 Dark Sigils . You can now refresh the area to obtain Anri’s Straight Sword where you performed the ritual and the Chameleon spell near the Pilgrim’s location.
- Anri's Straight Sword