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It's actually just a bug in how YouTube handles video redirections.
The account that uploaded that actually found and exploited a similar bug back in 2008 or so.
Nothing really satanic about it, it's just people creating spooky content and finding creative ways to propagate it.
Read the comments.
There's a channel called "watc".
When you remove the h, it confuses YouTube and sends you to that channel.
Whoever started the channel "watc" has it set up to redirect you to the 666 channel.