What happened has set the grounds for not just one but two really cool twists later in the series. (And some interesting behind the scenes facts and rumours) 😉
Since no one answered you, that black ooze shaped like a man is called Armus. He is the alien who kills the original security officer Tasha Yar in the first season.
What's interesting to me is that Marina Sirtis was originally cast as Tasha and Denise Crosby originally cast as Troi, but their roles were swapped. I'd love to have seen that version of TNG.
I don't know of anything else she's been in that she's played it tough, but I doubt they would have cast her that way if they didn't initially seen something of that in her. She certainly has the presence for the role if her outgoing personality at conventions is any indication.
Considering I have been called "overly stoic", "unsentimental", and "unemotional" by romantic partners, and my therapist tells me it isn't healthy to bottle up my emotions, I may just have seen myself somewhere in there.
