"thank you dark souls" is often used when dark souls players has something bad or a glitch happens to them
"ah fuck i died, thank you dark souls
"Thank you, Dark souls" is a popular phrase invented and most famously used by the well-known youtuber "videogamedunkey".
It's often used in bullshit situations, or otherwise unfair scenarios.
Daniel: Watch this, I'm gonna parry this fool!
*fails parry*
Daniel: Thank you, Dark souls