“As we worked on the Infinity Stones’ story, it became clear the story was much bigger than we could contain in the Guardians of the Galaxy series,” said editor Jordan D. White. “It starts with the Guardians, but the story extends out into the entire Marvel Universe, with stones popping up in some very surprising places. Countdown is the next step in the story…but as the name implies, it’s leading to something even greater.”
"As the hunt for the stones begins, a new weapon of unimaginable power is being forged…and it’s a weapon like nothing the universe has ever seen!," reads a Marvel press release. "What is its purpose? And who - or what - is the destructive force that will be unleashed on the world? The race for power in the post Secret Wars universe has begun, and its search will impact every Marvel character from the street to the cosmos, from the Avengers to Spider-Man to the X-Men, even bringing about the end of the Guardians of the Galaxy!"
The Infinity Stones were destroyed in the build-up to 2015's Secret Wars event, but four of them have turned up (in one form or another) in recent "Legacy" titles. From the cover shown above however, it looks like by the event's inception they end up in the hands of Wolverine, Captain Marvel, Gamora, Loki, Magus, and a Super-Skrull.