Well, what's just stopping him from sneaking up on someone? He looks human enough, and once someone/something gets close enough for him to grab I don't see why he wouldn't just be able to suck out their brains?

The Brainsuckers in Bloodborne are pretty good at this, and are basically Mindflayers.

[hider=Brainsucker sucking brains][img]http://vignette2.wikia.nocookie.net/bloodborne/images/2/20/Bloodborne%E2%84%A2_20151014084103.jpg/revision/latest?cb=20151014065301[/img][/hider]

He'd have to be smart with it, certainly, but once something gets caught by that I don't realistically see them getting away since [i]he's eating their brain[/i]. Plus, he could theoretically bind something with telekinesis, given its strength was weaker than his mental abilities.