It's a Creepy Juniper or something plant. Can't just dump mulch on top of that.
Yah, it's this thing. A rug juniper.
It looks kind of innocent in this Googled pic, but it's like a friggin thick, ruglike stalk, and it seems like a humongus pain in the ass to dig up, so it's left, but the grass is growing up through it and it's a bitch to maintain that. I dunno.