This MacenWolf release from yesterday by Serpens follows a simple theme; the number four.
These ports include three games each called 4th Encounter (One by Clubey spanning 10 levels, and two connected releases by an unknown author spanning 10 and 8 levels respectively).
In addition, ports for some other games that follow the theme are included in the release. These include a 15 level game by Clubey titled The Forth Riech, and Four Quality Levels, spanning the expected number of maps.
Four Quality Levels is credited to Tomato1044, TSmoovy, and Carloscont, but is speculated that they could all be aliases of the same person.
You can read about and download these releases from the associated ModDB article, and the games can each be played using a copy of either MacenWolf: The Second Encounter or MacenWolf: The Third Encounter, updated to the latest version.