My eldest DS went through this when he was a toddler, and they don't call it night terrors for nothing - it's very frightening to witness, so you have my sympathies milliec.
When my DS had his terrors, he would scream uncontrollably, go as stiff as a board so I couldn't gather him up to cuddle him, and he would somehow find enormous strength from somewhere, to the point where I found it impossible to even hold him let alone try and console him.
It was most unpleasant, and this isn't probably what you want to hear, but all I could do was let it run it's course. I always sat with him until he'd calmed down enough for me to actually hold him, then finally he would quieten down and go back to bed.
In the morning, he knew nothing about it, which I suppose is a blessing.
I can't really add any more I'm afraid. Suffice to say that it wasn't a very long-lived phase, thank goodness - maybe that will be a crumb of comfort for you.