He stands out right away. It's not that he's dressed all in black; most of the party guests seem to be wearing black and white. It’s his pale face that catches your eye, his deliberate approach. His attention is fixed on our everyman, to whom nobody else is paying any attention. And nobody else notices the mystery man either.
He never blinks. Once he makes eye contact – at which point the background music fades into a cone of silence that feels downright oppressive – he never once looks away until he leaves. In fact, he barely moves at all, and he's shown in this tight closeup that makes the stare even more unsettling. AND there’s a light reflected in his eyes, so in addition to being uncomfortably intense, his stare has a manic edge to it that’s only sharpened by the way he never quite stops smiling. If you can call it a smile. Despite the gleeful absurdity of the scene, the mystery man does not look like he’s joking. The expression is pure threat. Utterly predatory.
He speaks heavily, deliberately, without emotion. He leaves long silences before answering a question. He doesn’t use one word more than necessary, and gives a suggestive, leaden weight to some of them – I’m there right now. At your house. Ask me.
And WHILE being uncanny and threatening, he’s also pulling an inexplicable stunt that involves invading our everyman’s home – everyman doesn’t seem particularly disturbed by this exchange until he actually hears the mystery man’s voice on the phone and realizes he’s really there. The mystery man doesn’t explain himself at all, except for that one line: You invited me. It is not my custom to go where I am not wanted. Which has ALL the sinister mythopoeic undertones, especially when his only response to “Who are you?” is a fucking terrifying laugh made EVEN SCARIER by the echo on the phone.
I don’t even recall whether he ever shows up again in the rest of the movie. I think maybe briefly? Just long enough to imply some sort of connection or continuity; I don’t think he even speaks. You certainly don’t ever find out who he is or how he’s involved with the freakiness that follows. The movie has the same nightmare-like quality as the first Silent Hill - it makes just enough sense to imply that there is in fact some sort of internal logic at work, but not enough that you can sort out what’s actually going on.
Regardless: I love this scene all on its own. It is downright iconic.