Issue 25 of d12 Monthly is jam-packed with a lot of content and contains the following feature articles:

But Where Does it Go? – All about sewers and their construction, including game effects for each of the dangers.

It’s a Dirty Job – A new OSE (Old School Essentials) class: the rat-catcher.

It Came from Down There – Some new creatures and a new twist on some old ones.

Hey, This Has Saved Me A Few Times – A table to create new minor magic items.

Forgotten Underworld – A list of other places that could be under a city. Complete with weird and dangerous inhabitants.

The Under City – A new adventure location.

And much more!

It's also the third in the Settlement series of issues.