It is a space themed game but Demons come through portals (I think) to attack the players. Players have options to attack each other, or trade, other options. I remember enjoying the game but for the life of me cannot think of the title. I know this is vague but if you have heard of a game with these themes please let me know. Thank you.
There's a few possibilities that I can think of but, none quite fit the bill.
The Doom Boardgame had demons (of sorts) in space but, I'm not sure there was a trading mechanic involved. Claustrophobia had demons but, no space theme and no trading. So, vague matches bit nothing all that close.
When did you play the game and, could you possibly describe the box art? Might help in tracking it down.