At this point, it's unclear if the "Blue Whale" challenge is a hoax or if it's something kids are actually doing but supposedly it targets those between the ages of 10 and 14.
There have been no reports of the Blue Whale in the United States but the Cyberbullying Research Cetner claims to have known about it since February and there are reports coming out of other countries claiming that kids have been participating in it. It starts by having kids inflict self-harm and gradually escalates from there.
The "game" works by...
pushing them into doing a list of pained daily tasks such as waking up in the middle of the night, cutting shapes into their skin, and, ultimately, committing suicide. “For the last 10 days, the player needs to wake up at an appointed early morning hour, listen to music, and contemplate death,” Bloomberg reports. “Those who get cold feet and want to leave the game receive threats, often that their parents will be killed.”