[Spoiler:] A certain NPC Invasion

I have not seen anyone else talk about this, if anyone has experienced this please please let me know. After killing Pontiff I returned to the Bonfire my status embered and walked outside the large door in the back of the church. Under my feet there was a message that read dark spirit ahead. I readied myself for the conflict but when I saw it I couldn't believe my eyes.

The summon said invaded by Dark Spirit Chosen Undead (Well it really said Chosen Und***) Now I thought it was a human at first but this person showed up wearing exactly what I was when I killed Gwyn in Dark Souls 1. I for the majority of my game ran around in Artorias's Armor with the Iaito and the Abyss Greatsword. The NPC fought me with the Uchi, Artorias's armor, and the Farron Greatsword, the obvious replacement for the Abyss sword.

Has anyone else fought their Dark Souls 1 character? I am playing on PC and have a save file with a completed Dark Souls 1 game on it, did DS3 parse my save file? What is going on?