There are numerous moths in the Noctuid family that pupate in similar capsules. You would need to create a suitable environment in order to allow your moth to complete its metamorphosis so that you can see what it is.

Are they good for the garden?

How can simulate a good environment for them? Iv found them a little bit underground

The larvae are caterpillars; they eat plants. Some of our worst garden and lawn pests are in the Noctuid moth family. I'm consulting right now for a university campus that is dealing with a wicked infestation of armyworms (just one example) brought in with a large load of sod.

The adults are not usually very large and oftentimes rather drab. They do serve as a food source for birds, moles, armadillo, skunks, squirrels, predaceous ground beetles, amphibians, and bats.

Overall, in my experience as a professional, the bad outweighs the good in this case. However.....you can place about four inches of your dried garden soil in a glass jar, bury the pupa about an inch deep, mist the top of the soil with water, and cover with a lid poked with holes.

Place the jar in a warm, shady location. Perhaps a moth will emerge. If so, place the whole jar in the freezer for a few hours so that you can pull it out and take some pictures.

That is the only way to identify this insect.

It would be an interesting experiment. Would I do it if I found those in my soil? Nope.....

thanks for the reply, seems like those moth are not worth to keep...

eeeewwwww.....cockroach egg sac Just kidding