1) Go to Caustic Caverns, on the east of the map.
2) Find a Crystalisk monster called Blue.
3) Run north until you find a lone island with a single tree on it.
4) Head towards a bonfire on the island.
5) You will find a knight called Solitaire sitting near the bonfire.
6) This is mimicking Knight Solitaire from Dark Souls.
7) A phantom spirit can also be found nearby.

Note: You will lose a lot of health getting to the island so you need to be a high level or have Salvador activated.

Here is a video in case of any problems: