So I've heard about this for awhile, and I feel like I need to bring it to your attentions so yeah...

Basically, it's a website called Blue Whale, and this mentor or someone gives you a task for 50 days. It sounds innocent, like waking up early and stuff like that, but eventually it leads to you harming yourself, such as cutting a whale in your skin. And you have to send a photo of it.
At the end, it tells you to kill yourself.
And there's no way out of it. Once you sign up, they have your information and can track you down(I'm pretty sure).
So yeah, stay away from Blue Whale...