They say that a writer should research and backstory and take all the notes in the world, then file them all away and only directly reference about 10%, with the rest leaking through in dribs and drabs as the narrative progresses. I begin to think that the people who describe their character stepping into the narrative, be it story or campaign, for the first time should do the same thing, particularly if they’re late to the party. A mental picture is nice, yes. Being able to describe a character to the point where people can learn things from the description is also nice. Goodness knows I used to do that for fun with at least one of my players. On the other hand, you with the new character, I don’t need your entire biography the moment we meet. That goes for the flashbacks out of nowhere, the tendency to spill everything—but it also goes for the descriptions verging into purple as we walk into the blasted inn. Once you’ve gone for more than half a minute, I’m not sure I even care what color the character’s hair is. (I might make an exception for when I’m reading, but if your character description takes me half a minute to read, that’s probably a problem in and of itself. That’s pushing a page right there.)
Know the description. File it away. You’ll get to use it later. Right now we just want to get on to the vital question of whether these people we think through are going to be able to put up with each other.