What it does
I'm not familiar with "Blind Betrayal" as an official Magic: The Gathering keyword or ability. It doesn't correspond to any keyword in the comprehensive rules that I can reliably recall.
It's possible this is a custom or homebrew mechanic specific to a particular set, a card with "Betrayal" in its name, or perhaps a misremembered name. There are real mechanics it might be confused with—like Goad (which forces creatures to attack a player other than you), or cards involving theft and sacrifice that "betray" their controller.
If you can share the exact card text or where you encountered "Blind Betrayal," I can give you an accurate breakdown of what it does, the common rules pitfalls, and how it plays out in a Commander pod. I'd rather not invent rules and steer you wrong.
Iconic cards with Blind Betrayal
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