What is Stachybotrys?

Stachybotrys chartarum is a dark mold that grows on paper-faced materials that have stayed wet — drywall, some fiberboards — usually for days to weeks, not on a dry shower door overnight. It is one organism, not a category for every black stain in a cellar.

Only a lab can confirm it. Whether or not that is the name, wet drywall with growth gets removed under containment. The nickname should not change your urgency upward into panic or downward into a bleach wipe.