Item description:

This is a Deathrun map. I put it together by cutting out other parts of Deathrun Maps. Now that that's said. Don't complain about it.
Anyway, Run through the map and touch the blue Combine Monitor walls, called the Yotsu-Portals to warp through Yotsu-Space to the next corrupted world, where some pieces are removed and even replace with other peices from other worlds.