The Derwent company has been in existence for over a hundred years and Derwent pencils, both graphite and colored, are known for their quality. One of the range of colored pencils that Derwent make are pastel pencils.
Pastel pencils are softer than normal colored pencils and feel as smooth as velvet when you are laying down colored areas with them. They are great for blending and layering and the pigments combine easily to produce vibrant colors making the drawing process much more pleasurable. They still provide the control and precision one would expect when using a pencil even though they have a softer center.
You can purchase these pencils in a wide array of packs and color ranges, including boxes containing 12, 24, 36 and 72 pencils. A 12-set is probably going to be limiting in the range of colors it offers, though.