Importing DCS files
Desktop
Color Separation (DCS) is a version of the standard EPS format.
The DCS 1.0 format supports only CMYK images while the DCS 2.0 format
supports multichannel CMYK files as well as multiple spot inks.
(These spot inks appear as spot colors in Illustrator’s Swatches
panel.) Illustrator recognizes clipping paths in Photoshop-created
DCS 1.0 and DCS 2.0 files. You can link DCS files in Illustrator, but
you can’t embed or open them.

To
see DCS transparency interactions in the Links panel, choose Panel
Options from the Links panel menu and select Show DCS Transparency
Interactions.