Suggestions for how to tackle this mound of earth at the back corner of the lawn? A friend thinks it might be covering a sump pump, and suggested not to dig there.

It looks like from the color of the brick that at one point there was a lot of dirt piled up along the brick work, wonder if there is any possibility you could get any info from the previous owner

mmm, I bet the dirt on the wall is just where the bare earth splashes up.

I'm not sure what she meant by covering the sump pump. I thought sump pumps were usually in a pit inside the basement. (I don't actually know, our house predates them. It's...interesting in our basement)

Additionally, electric is (supposed to, by code) be buried much deeper than you would hit with a hand trowel.

In any case, I would probably dump enough compost and maybe other soil over it to make a proper raised bed. Plants like the drainage of a raised bed anyway. Compost will improve what looks like pretty iffy soil. Spray glyphosate to kill the weeds before you add new soil.

I don't think it has anything to do with a sump pump, unless it's covering some kind of discharge, and you should be able to tell that by following the mound.

It's really got the look of waste ground. I wonder what the eave/roof edge looks like above. I'm a concerned about what may be underground. It looks like maybe a gas line coming through the fence. And there seems to be a lot going on with the electric. Any exploration into the mound should be done very carefully. And that underground electric cable running along under the clips. From experience, I know underground doesn't necessarily mean above ground. I would certainly have had that in conduit.

There's a lot of slop-jawed electrical work in sight, and I'd address that as a priority before worrying about the ground cover.

You do have a very interesting 'rental' landscape between your front yard 'tree beheading' and the side yard 'weird raised area'. You could ask the landlord what's in the mound and what you can do there. You may not like the answer particularly, but at least you'll know. Any efforts will be better than what's there and there's the possibility that you'll get some help and ideas.

What???? It could happen.

Update: I'm planning to pull the weeds, cover with compost, and plant buckwheat seed.