Is it some type of mud nest built by a wasp or (hope not) termites? Someone suggested it might be some sort of fungus, but I think not since there is a symmetrical hole towards the bottom.
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Well… poke a hole and find out 
Ants is the other option.
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Be ready to run if it comes after you. Joking.
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On second thought, it might be a slime mold (not a fungus, but more like a fungus than a wasp’s nest).
Here’s a picture of something similar, but the color is much lighter -
(from NCSU Plant Disease and Insect Clinic’s blog post “It Looks Like a Dog Threw Up in My Mulch: Slime Molds - Harmless but Ugly!”)
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I think it is a slime mold that is old and drying out. I bet if you blast it with a hose a whole bunch of spore-filled dust poofs out. I get it all the time in places I use arborist chips. My understanding is that it is harmless, possibly beneficial in that it is breaking down the chips faster.
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I was thinking I would try a gentle watering to see if it grows/changes. Then I’ll know if it is a slime mold & if it is, no more worries about termites.
I have seen those happen in mulch several times… they start off sort of creamy yellow in color when they are initially erupting… but as they dry and harden they get darker, brownish… nothing to worry about. Scrape it off if you must, just let it rot and compost if you want… it will eventually.
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Putting mulch against your bricks is a good way for termites to get access to your house. Not saying it is termites, just a tip.
It’s fungus. I have had this around my house a few years ago. It went away over time. It seemed to come when it was really wet and humid.