These piecescan be used with the smaller 2x2 Lava banks pieces, or work standalone to build a variety of rivers, pools, and gentle slopes. These banks are generally used in "negative space" builds where some sort of texture - such as a Terrain Tray, Phantasmal Filter,Battlemat, or even a graphic you've printed out yourself - is used as a base and then surrounded by these pieces to reveal water, acid, or some other hazard.
These pieces are also ideal if you want to gently raise up one floor height in your build - such as transitioning from a section built directly on your table up to a section built on top of a Battleboard or DF Light Panel.
Hellscape sets are cast intranslucentDwarvenite. You can light them from below with DF Light Panels(sold separately).