Of Circles and Rings is a short story written by Tom Lynch. It was first published in the 2014 anthology The Dark Rites of Cthulhu, edited by Brian M. Sammons.
Description[]
Pete Jones, an up-and-coming martial artist, thinks he has found in Shun Jian someone who can teach him a new method of fighting which will make him unbeatable. Unbeknownst to Pete, his "teacher" is actually a millennia-old cultist of Yog-Sothoth, and his god requires sacrifice to continue granting Shun eternal youth.