Some sort of black ooze

As the smoke clears, the shape seems to collapse in on itself. When it's gone, all that's left is a large puddle of some sort of substance. It's not water, that much is obvious. It actually looks like it's halfway between a liquid and a solid, like gelatin. It's pitch black, too, to the point it looks kinda like a hole in the world. The only clue that what you're looking at is actually alive, rather than just being the mess made my someone else's familiar, is the subtle ebb and flow of the puddles edges, the rhythm of which matched your own breaths.

To be honest, you're not entirely sure what to make of... whatever it is. But you do notice that the citadel has become quiet. Eerily so. Looking around, you notice that everyone is simply staring at you with widened eyes. You turn to the Wizened Wizard, your eyes desperately asking a simple question: "What?"

Unfortunately, you don't get an answer. Or, at least, not one you understand. Instead, the Wizened Wizard merely nods and mutters, "Interesting. I suspected as much." You're about to ask what's so interesting, but before you can, you feel a sudden coldness envelop your foot, and you feel an odd sensation of fear.

Looking down, you see that the black slime you had summoned had wrapped part of itself around you. You infer, from the fact that you didn't have anything to be afraid of and that the fear didn't start until contact had been made with your familiar, that you were feeling the slime's emotions of fear. "Well, that won't really do," you think to yourself.

Crouching down, you bend your head towards the slime and put on what you hope is a warm smile. With a soft voice, you begin speaking to your familiar. "Hey, it's alright. There's nothing to be afraid of. I'm Tobias, your summoner. Welcome to your new home." You finish by extending your hand, which was a habit you had picked up for whenever you welcomed somebody or introduced yourself.

For a moment, nothing happens, but eventually the puddle stretches a small tentacle out and wraps itself around your hand tightly. The sensation of fear dissipates, replaced by a warmer feeling that seems to be a mixture of relief and happiness.

The Wizened Wizard nods towards one of the assistants, who hesitantly escorts you off of the summoning circle. As you walk back to your seat, your familiar slithering along the ground behind you, you notice that everyone seems to be putting as much distance between you and them as possible. Sure, you were never popular, but this was ridiculous! As you sit down, your slime puddling around your feet, a thought comes to mind:

"What if they're avoiding me because of the slime?"

You already have no clue how to take care of a slime. Now, in addition to that, you'll have to research black slimes in particular to figure out what's up.