It had appeared sometime overnight.
Later over the next few days, we had 6 more attacks: some in back and some out front.
From Wikipedia: "Slime mold or slime mould is a broad term describing some organisms that use spores to reproduce. Slime molds were formerly classified as fungi but are no longer considered part of this kingdom. Although not related to one another, they are still sometimes grouped for convenience within the paraphyletic group referred to as kingdom Protista.
"Found in a wide variety of colors, more than 900 species of slime mold occur all over the world. Their common name refers to part of some of these organisms' life cycles where they can appear as gelatinous "slime". This is mostly seen with the myxogastria, which are the only macroscopic slime molds. Most slime molds are smaller than a few centimeters, but some species may reach sizes of up to several square meters and masses of up to 30 grams "Whatever the science, I think it's kind of creepy.
It seems to be in the mulch that we applied this year. Yuck!
Here's a video of the stuff: not mine, I assure you.